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JOURNAL
OF THE
ROYAL MICROSCOPICAL SOCIETY;
CONTAINING ITS TRANSACTIONS AND PROCEEDINGS,
AND A SUMMARY OF CURRENT RESEARCHES RELATING TO
ZOOLOGY AND BOTAN YD (principally Invertebrata and Cryptogamia),
MICROSCOPYW, Sc. LIBRARY NEW YORK Ldited by BOTANICAL
GARDEN
FRANK CRISP, LL.B. B.A, One of the Secretaries of the Society and a Vice-President and Treasurer of the Linnean Society of London ;
WITH THE ASSISTANCE OF THE PUBLICATION COMMITTEE AND
A. W. BENNETT, M.A., B.Sc., F, JEFFREY BELL, M.A, Lecturer on Botany at St. Thomas’s Hospital, Professor of Comparative Anatomy in King’s College
8. O. RIDLEY, M.A., of the British Museum, asp JOHN MAYALL, Jon., FELLOWS OF THE SOCIETY,
ser. fl—VOL. lls PART 2.
PUBLISHED FOR THE SOCIETY BY
WILLIAMS & NORGATE, LONDON AND EDINBURGH.
ESS 2:,
The Journal 1s issued on the second Wednesday of February, April, June, August, October, and December.
Phy ;
$ Bic Ser. II. : To Non-Fellows { Vol. 11. Part 4.} AUGUST, 1882, |" Price 48.
JOURNAL
OF THE
| MICROSCOPICAL SOCIETY;
CONTAINING ITS TRANSACTIONS AND PROCEEDINGS,
AND A SUMMARY OF CURRENT RESEARCHES RELATING TO
ZOOLOGY AND BOTAN YT (principally Invertebrata and Cryptogamia), MICROSCOPY, &c-
a
—,
Edited by
FRANK CRISP, LL.B., B.A., One of the Secretaries of the Society and @ Vice-President and Treasurer of the Linnean Society of London ;
WITH THE ASSISTANCE OF THE PUBLICATION COMMITTEE AND
_A. W. BENNETT, M.A., B.Sc.,~ ¥F, JEFFREY BELL, M.A., Lecturer on Botany at St. Thomas's Hospital, _. | Professor of Comparative Anatomy in King’s College,
$0. RIDLEY, M.A., of the British Museum, ssp JOHN MAYALL, Jex., , FELLOWS OF THE SOCIETY.
' WILLIAMS & NORGATE, : : LONDON AND EDINBURGH.
. PRINTED BY WM. CLOWES AND SONS, LIMITED, } {STAMFORD STREET AND CHARING CROSS.
C2) JOURNAL
OF THE —
“ROYAL MICROSCOPICAL. soommry.
Ser. 2.—VOoL.L. Ile PART 4. (AUGUST, +BB2)
Cun iers TRANSAOTIONS OF THE: SooimetTy— 2 < rae oh oe PAGE
X.—On some Micko-oRGANISMS FROM “Ravwarm low aa Ham. pe bets By R. Li. Maddox, M.D., Hon. F.R.MS;&. .. 2k. 449°
XI.—Tae Repation or APERTURE AND Powsr IN THE Mronoscorr ; (continued). By Professor Abbe, Hon. F.R.MLS... .. .. 460
X1I,—Descrierion or a Suupia Pray or Impeppina Tissuus, For Microtome Curtine, in Semi-punpep Unenazep Printaye Parrr. By B. Wills Richardson, F.R:CS.L, Vice-President _ University of Dublin Biological ‘Associa PAE he anes ece NM Shy. Le Bie
XIL —NotE on THE Rey. G. L. Mus’ PAPER on Diaroms: ji. Nes Peruvian Guano. By F. Kition, Hon. F.RMS... .. .. 476
Summary or Curzent ResEARCHES RELATING TO ZooLoay AND Borany (PRINCIPALLY InvERTEBRATA AND Cryprocamma), Micro- scory, &c., INCLUDING OniGinaL Communications: FROM FEutows AND: OTHERB. "oS. foc) wa 26d SS es coy eat > ee ieee ea eae eS.
_ ZOoLoey. Sep ee OR BaP aD
Division of Embryonic Cells in the Vertebrata, 2 s00 2 Si Des gure Pam 7, ATS Genesis of the Egg in Triton .. —.. eerie, risiry yy Sane Bryce 7 Rage Formation: of Bibrine se) sed ide) we hse se Mae vo tp ae eee ina ee Bi pale New Blood-corpuscle . en eee A RRR io eons MRR aE OD Life and Death in the “Animal Organism .. Jo Wika eet wt heh Gemeeieed Cast FS Pelagic and Deep-Sea Fauna ., sede aS phea tae Ne Gad tebe A es tL: Anatomy and Classification of the Cephalopoda LORS eas A ee gee eae ES Ink-Sac of Cephalopoda .. _.. +: oe beet obats gay ae oe Og. Sense of Colour in Cephalopoda es Pipenmeninie, mkt F-sceary a yee ible tS
‘ Foot’ of certain Terrestrial Gastropoda PE SMS kG IT eRe Te Mucin of Heliz pomatia .. .. wee ER age 0k apes Mike wipe itr tatet eet Rhodope veranii .. — «. Be Fr abies) GEM CK Beli chibe SMS RMI ia hele ae En
Vest.Cells%in Ascidian.Ova SL meen earn are IPSS S wicstam I a Embryology of the Bryozoa Paes eee Pa ae Tamar y HUE ahs eran: ee Nt ty
New Adriatic Bryozoa«. iF eel, SOE Sensations of Sight conveyed by ‘the F aceb-eye @ igs 88 aad i) Pe oe |) ae Nervous System of the Strepsiptera.. «. as ver ae) 499
Insects which injure Books VR ae oe ee alan A PENRO ECO PEM ee ae Ra ROD
Formation. of Galle: oe i iyioe ter mabe ad aby Vola Chat eda tae es
Anatomy of Phalangida .«. reer ty aaltes et AS) | 5 Aree Scent-glands of the Scorpion-spiders (Thalyphonas) PGi ne Satm tchios Metab aera tee, Classification of the Brain of Crustacea...’ .. Bb da ye en a agen oe Unpaired: Bye of Crustacea): 50)... oar ay ees ian) ole) aa eee PE Blood of the Crustacea... Bago igs Sg gh A a aE ee
Pyloric Ampullz of Podophthalmate Crndacea se sh pee - 805
Heterogeny of Daphnia. 2» es ewe tee te ae wn a 906 i
ee a eee RAE HBS MK
= ‘Summary or Current Resmarones, &c.—continued.
: PAGE
: Notodelphyide .. (ARS Sita ie A 506 rare Organization of Trilobites .. UG Tones SORT Ta oO Tet Papel Set Chemical Composition of Tubes 0 af On Onuphi He SNES ey hey eee ROT RR Nematotd Hematozoon from a WILE Ae ESOL ee SERS oe OM Development of Marine Planaria: .. + ee te pete te ne we BOD
Eyes of Planarians .. SAR Mahe Se PMRCONE Lte hee Q he Sek LO
Development of the Orilionectida. Sie GaN SGN Se Rad ORR AS aiaae TAR ei
, Byes of Rotifers .. .. as 65 EN See One ata eo DE ge ees Cee Ee
Anatomy: of EHolothurians: 3. ise 58 eek. fee tap tees anes ey, ee OAS Hybridization of Echiinotdea 4+ ss ee ee ne ne pe we ee ne BIB
Variation in Asterias glacialis ... .. CVE be eke cow OLS ~ Development of Calcareous Skeleton of Asteroides - PPE Sr a RUE ELC RUS) 3 Development of Ziquorea .. RIESE rial amass IR PETe GL eee Fi)
Hybridization in Fresh-water Sponges UR Seer UNE i Py he ees Boring Sponges Barrie § Cae pee N aw Neal? oa. t Rae RS aN RRR, eee OLO
De Lanessan’s Protozoa .«. SEU y dys Rage Peipaning ait ipta, ad one e mundo Kents Manual of the Infusoria es, SREP sae gt SE ERO eee IR Flagellata .. ies Ae OLS Cell-parasite of Frog’ ¢ Blood and Spleen (Drepanidium ranarum) SAR ieee Sy Development of Trypanosoma... «+ +. Dae, Pett aby Spee UOeD
: _ New TE GOUPINAE Ge ek had SR oe ae aa Seg PAP pee Nance ae Oe Chemical Difference between Dead and Living Protopasm (Fig. es +» 522 * Killing of Protoplasm by Various Reagents .. ¥ Sek em ree Apical. Cell-growth in Phanerogams..0 6 ek ne te ee oe ee we 528 Development of Bordered Pits .. Se ene TOee ‘Development of Tissue as a Characteristic of Groups of. Plants same aeY | Stomata of Polycolymna Stuarti .. Pee ep ae HOE Properties and Mode of Formation of Duramen .. sl ft be oer) OD History of Assimilation and of the Functions of Chlorophyll PARRY Theoretical View of the Process of can zie og fviga. ew n dae
_ First Products of Assimilation... — .. Sects (om Subba ee NP RS anh eae ae - Absorption of Metallic Oxides by Plants... 526 Decomposition of Calcium carbonate tn the Bre of Dieters Woods 527
* Hypochlorin.. .. oe big ak Sales sole Sooke (aes ORS
- Latex of Euphorbia Lathyris a ges) ag ee OSE Darwin's so-called “ Brain-function: ” of ‘the Tips of Roots « oR a RaRA edt hee. OGD Aerial Cultivation of Aquatic Planis' .. pe Saat phi pe ye Seon TNGerlecOrOUs: LLGMtA Seve. vege iube oy ate oar EARS A AAS IESS Oe ee) OBL Climbing Plants ...:. bit Re GR ww ety s 12S Sap ce hy ae Ae ls ope RPE Power of Movement in Pigteis \ Siskaeo Sia ae si ep Sk: Nr Pied er bee ODE Electrical Researches on Plant Forms... Seat neya ee WN ee ate Oe
Electromotive Properties of the Leaf of Dionza .. x dee dette shea woe ~ Influence of a Galvanic Current on Growing Roots... ws ee ee 583
Schizeacee .. . SO AP Seah a che She tack Oh lasek A TRAN OR Branched Sporogonium of @-Moss .. ee ee ete en Tr aeoer tae Influence of Light on the Thallus as Maréhantia. SS eaety ave OEM Oe RENN «5 Goebel’'s Musciner — .- Fite CW IRS ped Shee pk ae Doe Development of the Cortez Si Ohta ce Sgt gS ey GN OBB Ustilaginer.... ir raS ek ts st Aiadas a ste ig lo. by we OG
Unobserved Sensitiveness in Phycomyces Rae Oba t ans Guan as TE CaaS gan pe OD Beltrania, a New Genus of Heghomyeates Pa ah aaa ait ier Ur Se
Chemical: Composition of aes * Pees ahr ae Visie te a eek, OUR Salmon Disease... «s 538
Formation of Saccharomyces in - Nutrient Fluids containing various Pro- portions of Nitrogen .. han hues ve, SSE Morphology and Genetic Relationship of Pathogenous E Bacteria... 1. 541 Bes - “Pathogenous Bacteria... °.. Boe DS ves Mae sR Tec 2 Rak 3 Bacterium of Charbon .. he! apeedp ate) ag aaa ve TC wok URS ee pa Pe Connection of Bacteria with Ferments Mane teey 2 hak sake or ug eats Gar base taek SE Life-history of Cora... sR pak s Tete ete) ulus eles te ces t kaeee
Minks’s Licheno-mycological Symbols ib EUR PRT Spee Sle ae ak arya c the Symbiosis of Alge with Lower Animals... 2. ee tee ae we ee, 4D Division of the Cell-nucleus in Spirogyra ogres PME GHy aes Sends LORD
(ay
‘Summary or CURRENT Reseanonns &e—continued.
PROCEEDINGS OF THE SOCIETY phi ace aieh NIB eee goat eee
549
ae
909
O78
BI 878 aT:
Pi aoe PAGE. Batrochospermimn |. 0 OC a eon eck ae eee tec Oe iene tae CAE New: Beg geet. os te a OR EP Ie pti ay Saat ay een HEA (MGM YP EN a on Soe Mea Eee Cn, as oe a ae Sede he ee epee ae OE Schizophyces. SANT We OF askin: hae seine Oa Sa ReMi aint ee OURERS me ae i neem aes OME Ly Mobionaf Diabaig: 252. GO gh POL ag a oe sae eg ee : Microscopy. Pei g sir: ae Re Lossner’s Tele-microscope .. .. Lk ON Jae og eh aia! DEE Prazmowski’s Micrometer Microscope (Fig. 91) ee erg th Simplified Reading Microscope for horizontal and vertical sive ROW Nea, Swifts Tank Microscope (Fig. 92) .. Rapier etree. Oa Leasdale's Field Naturalists Mieroscope (Figs. 93 and 94): bce Trae S Nes, BESET Steinheil’s Achromatic Eyepieces (Figs. 95 and oy Si Vides Mawel ales Aiea «eka New Combination for Objectives 2. uae Gah SGth saana aay tue et RO DE. Fluid for Homogeneous Immersion .. Sol Shurley’s Improved Slide for the Examination of Gaveo Dialer Orig ” 551) Hardy's Compressorium (Fig. 98) -... 4. ws aaa hae Rane ee Bulloch’s Diatom Stage ~ .. Soe aa Re aden eer rede Substage Fine-adjustment (Fig. 99) .. Rae atno Pancreas ee ee at ES Sidle’s Centering Substage (Fig. 100) ied aps OOS Mounting for the “Woodward” Brink (Figs, {01 and. 102)’. magnesia rh ag 3H Prisms versus the Hemis; herical Leng as LUNN ie AOD nae ues 4 Pate 3411 Hadial Tail-pieces’— .. em ear cael wey y Electric Light in Microscopy Pigs 103 and 104). TERCERA ek OEE Black Backgrounds .., pets epi ey Apa se BO Micrometrical Measurement by means “of Optical Trages OF eh a irs Be aay ~ Malassez's Improved Compte-globules (Figs. 105- ae her dat haipeeanaarat Cutting and Mounting Microscopical ones Bao bh hae k BOL ay eee EE Preparing Blastoderm of the Chick .. se. 41 ee eu ee te te ea TO Preparing Embryos of Insects .. *. eb Yale SN Ree eae iaabac Ce Collecting, Staining, and Photographing Babteria say Cc ee eee OTL Ehrlich’s Method of Exhibiting the Bacteria of Tuberculosis Wi fyam Siders DIS Preserving Infusoria and Amebe 6. te cee ne ee eee TA Preserving Protozoa. .. Cae “a ahe eA eee Bac tae ne Ege Staining the Nucleus of Living Infusoria... PR ey tee eet Mr Lan em Double Staining with Carmine and Anilin Green .. Ry ied eRe egies AOE Cutting Sections of: Coal: vi) 5. Sa Gal Say eae ee wa ee a ONE Bections of Miea-sohiiat 56a eee, a an ae eee etee. OTS Paper Cela riot oe ags® ook icp ae pix decal eae a el ga ane ike eel ea Wax Cells ne ae . oe SAE oe Rk we pat 5 ee ae bacpcare cur 578 Miller’s Caoutchoue Cement. sss es tn ae Mounting in Phosphorus ee aham nie gang Seal on eikan Naas eee eee Vacuum-bubbles in Canada Balsam . Pea Nias i WR Soin Sh RIO OA Patt eR ole Mounting Moist Objects in Balsam. jodi) aan gs alga aw © toe chee eek (DOA | Moisture in Dry Mounts’ .. °.. as Sa pV gE A Ge ea ea Dammar Varnish j yb 60 enw iy Sy te neon ae eee Oe Cleaning Used Slides and Covers oUg og ol Eadie” aah hE Cae ay RE AI BE Resolution of Amphiplewra pellucida... 24 ce ce ae ne ak ne ee BEY Microscopie Examination of Wheat -flour .. x5 ine Weds 3 pe etek DOS Destruction of Microscopical Organisms in Potable Water ye We tga on 2 OOD. Public Lectures in. Microscopy *+s 55 os. a a ke he nee ae 585 589
(8) AHopal Aicroscopical Society.
“MEETINGS FOR 1882, .
AT 8 P.M. 1882. Wednesday, January... 6. we % FEBRUARY .. sein §
(Annual Meeting for Blection of Officers and Council.)
us Marcu 8 Be APRIL .. 12 y May | 10 5 JUNE 14 be OcTOBER FOS SIERO Peake Bs OMe Supe > | 5 NovemBEeRr
. DeowMBeR Hi Fe Se PAS
THE ‘SOCIETY’ STANDARD SCREW.
The Council have made arrangements for a further supply of Gauges and Screw-tools for the “ Socrery” Sranparp Sorew for Ossxorrves.
The price of the set (consisting of Gauge and pair of Screw-tools) is 12s. 6d. (post free 12s, 10d,). Applications for sets should be made to the - Assistant-Secretary.
For an explanation of the intended use of the gauge, see Journal of the Society, I. (1881) pp. 548-9.
ADVERTISEMENTS FOR THE JOURNAL.
Mr. Cuartes Burncowsg, of 75, Chancery Lane, W.C., is the authorized Agent and Collector for Advertising Accounts on behalf of the Society.
(6)
“COUNCIL,
ELECTED 8th FEBRUARY, 1882. re
PRESIDENT, : Paar. Pe Marin Duncan, M.B., F.RS. ~
VICE-PRESIDENTS.
Pror. I. M. Baxrour, M.A. E.R. S.. . Rosert Brarrawaire, Esq., MD. MBC. S., FL, g. Rosert Hupson, Esq., E.RS,, ELS.
JoHN WARE STEPHENSON, es BRAS. a
TREASURER, Sa Lions 8. ‘Beare, Esq., MB., FRCP, ‘ERS.
SECRETARIES.
OHARLES Srewarr, Esq., MLR.CS.,. FLS. oe Fran Crisp, Esq., LL.B., B.A, VP. & ‘Tras. Ls.
Twelve ather MEMBERS of COUN cI.
Lupwie Dreyrvs, Esq.
CuAaries James Fox, Esq. Jamus: GLAIsHER, Esq., F.R.S., PRAS. J. Wirt1am Groves, Esq.
A. pE Souza Guimarazns, Esq.
Joun KE. Inaprn, Hsq.
Joun Mayatn, Esq., Jun.
Aupert D, Micwazrn, Esq., F.L8. ; JouN Minuar, Esq., L.R.CP. Edin, F.LS, Wii1am Tomas Surronn, Esq. Freperick H. Warp, Esq., M.R.C.S.
T. Caarrens Wurtz, Esq., M.R.CS., FL, 8.
Ne, eg I. Numerical Aperture Table.
. The “Arerrure” of an optical instrument indicates its greater or less capacity for receiving rays from the object and ee transmitting them’ to the image, and the aperture. of a Microscope objective is therefore determined by. the ratio’ between its focal length and the diameter of the emergent pencil. at the plane of its emergence—that is, the utilized
_ diameter of a single-lens objective or of the back lens of a compound objective.
This ratio is expressed for all media and-in all cases by sin w, n being the refractive index of the medium and ~ the
: Semi-angle of aperture. ‘The value of n sin u for any particular case is the ‘numerical aperture” of the objective,
__*~Diameters of the Angle of Aperture (= 2 1): Theoretical | 5, Back Lenses of various oo Ilmi- Resolving ene-. Dry and Immersion | Numerical Watéer- | Homogeneous-| nating | Power, in _ | trating ‘Objectives of the same | Aperture. Dry cae Zevsneasion Power. | Lines to an Inch.| POWer- Power (3 in.) (w sin w= a.)'|: Objectives. } ob iectives,|° Objectives. |. (a4). |~ (A=0°5269 u (2) from 0-50 to 1-52 N. A. (m= 1) l(a = 1-33.)) (m= 1°52.) =line EK.) a Beta crear eal 1°52 180° 0’ 2:310 146,528 “658 1:50 161° 23" }2°250| 144,600 “667 1:48 | 158° 39° }2-190 |. 142,672 676 1:46 | 147° 49" |2+132) 140,744 “685 1°44 | 142° 40’ |} 2-074; 188,816 “694 1:42 138° 12’ |2*016| 136,888 “704 1:40 - | 134° 10’-/1-960! 134,960 “714 1°38 - 130° 26’ |1°904| 138,032 “725 1:36 126° 57’ |1‘850) 131,104° | +735 See 2 123° 40’ | 1-796! 129,176 - | _-746 : © 9’ 122° 6 1°770; 128.212 “752 130 tae me io 33) pee ats pe 1:30 155° 38"; 117° 34" |1-690). 125/390 | . «769 1:28 148° 98'| 114° 44" | 1-688. 123,392 “| -781 . [o} Ua) oO rit . § Pied ee POGUE Rete CRO Barer keer 1:22 133° 4"; 106° 45’ 1-488; 117'608 | +820 ; >] 1s fase. 8/1 40 en |4-aoat 18/758. | ee 1:16 121° 26’; 99° 29} 1-346) 111,824 “862 is Tee eee rd rp ae ihe ai ee r| “7 | 4-2: 7, 4 Be pon eS) Las meee 1-06 f wos art Se oe. 1 aba 102,184" | +943 1:04 102° 53’| 86° 21’ | 1-082! 100,256 “962, - 1:02 — i 100° 10"|- 84° 18’ |1:040| 98,328 |- -9g0 1-00 |} 180° 0 | 97° 317} 82°17’ 1-000! 96.400 | 1-000 0-98 .| 157° 2°} 94° 56’ 80°97"! ~960) 94,472 | 1-020 0:96 147° 99" | 929 24)" 78° 20" | +992). 92,544 |-1-042 0-94 +.140° 6’ | 89° 56’ 76° 24’ | -884| 90,616 | 1:064 092 | 138° §1’ | 87° 32'| 74° 30’) +846|. 88,688 | 1-087 0:90 128° 19’-|-85° 10’| 72° 36’ |- -810! 86,760 | 1-111 0°88 123° 17% 82° 51"|. "70° 44’ | 774." 84,832 | 1-136 0:86 118° 88’} s0° 34’| : 68° 54’ | +740; 82,904 | 1-168 0:84 114° 17’ | 78° 20"! 672° 6’ | --706! - 80,976 }'1-190'- 0-82 | 110° 10’| 76°. 8’) 65° 18’ | +672) 79,048 | 1+220 0:80 106% 16’.| 73° 58'|.. 63°31"; +640|. 77,120 | 1-250 0:78 102° 31’ | 71° 49"|~ 61° 45’ | -608| 75,192 | 1-282 0°76 98° 56’ | 69° 42'| , 60° ..0' | +578) 73,264 -| 1 B16 0°74 95° 98! | 67°36") 58° 16 | -548|} 71,336 | 1-351 0°72 92° 6’ | 65° 82'| 56° 32’ | -518{/ 69,408 | 1-389 0-70 88°51’ | 63° 31’) 549-50" | <490|*. 67,480. | 1-429 0:68 85° 41’ | 61°80’! 53° -9” |. -462 65,552 1°471 0°66 82° 36’) 59° 30’) 51° 28’. | -436} . 63,624 | 1°515 0:64 | 79° 85" | 57°.31’) 49°48" | -410/- 61,696 | 1:°562 0-62 76° 38'| 55° 34’). 48° 9’ |- +384! 59,768 | 1-613 0-60. | 73° 44" | 53°38} 46° 30° |. -360!. 57,840. | 1-667 0:58 70°. 54’ | 51° 42’| 44°51’ |. 836] - 55,912 |.1-724 0°56 68° “6! | 49° 48’|- 43° 14/ }<314| 58,984 | 1°786 0-54 65°22" | 47° 54’) 41° 37° | +292) 52,056. 11-852 0-52. “62°. 40" |46° 2} 40° (0% | +270! © 50,128 | 1-993. - 0°50 60°. 0’ | 44° 10’| 38° 24’ | -2501 48,200 -| 2-000
Exampite—The apertures of four objectives, two of which are dry, one water-immersion, and one; oil-immersion, would be compared on the angular aperture view as follows:—106° (air), 157° (air), 142° (water), 130° (oil). |
Their actual apertures are, however, as 2 *80 “98 1°26 1°38 . or their numerical apertures.
Scale showing ||
the relation of Millimetres,
&c., to Inches, mn.
_and
em. ins,
ESTES PRG Se SO ACEI ARE BST IS, SURE) PETES A DASE ESTA Pee SAE FEC eel BRE bt ee eR SR Ee 7 —
‘= ] a
a
a
im
:
a | a a a tI mi | J rs a a @ m aS i a a | | 5 | | ml
000. =1 mm, 10 mm.=1 em, 19 om. =1 dm. 10. dm. =1 metre,
II. Conversion of British and Metric Measures. = = = = ~~
: . (1) Lineau eta roh SLMS ie ch Cpa Aa manna
Rs Micromillimetres, §c., into Inches, Go.) | * Znohes, &¢., into: we) ins, Bynes ele, Smee iene . hen ae Ceo ee
1 +000039| 1 089870} BL: yo 2007892) ine yy,
2 -900079.| 2 078741 | 52 2.047262 | 3 1-015991
3 000118} 3. 118111} 53: 2°0866383| =°5°° - 4.069980 _
4 -000157| 4. "157482 | 54 24126008}; 22322 4-g93918 5 +000197| 5 196852]. 55° B165874 | PP? 9. Ba 9977
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OBJEC- TIVES.
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EYE-PIECES.
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20 | 25 | 30 | 40
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* Powell and Lealand’s No. 2=7 +4, and Beck’s No.2 and Ross’s B= 8 magnifying power, or respectively >, less and }; more than the figures given in this column,
‘HENRY CROUCH 1s :
First-Class Microscopes. !
"Student's ‘Microscope.
‘New Family, and School : _ Microscope, — ;
\ | New Series of Onjectives,
Y New Accessories.
NEW ILLUSTRATED ae ON RECEIPT OF ‘STAMP, LED ABROAD FREE, ;
HENRY CROUCH, 66, farbleah London, 5 o.
AGENTS IN AMERICA,
JAMES W., QUEEN & 00., 924, es Street, Be v 8.
JAN 20 1903
NEW YO RK
BOTANICAL JOURNAL Ai Sesatnci OF THE ;
ROYAL MICROSCOPICAL SOCIETY.
AUGUST 1882.
TRANSACTIONS OF THE SOCIETY.
fe
X.—On some Micro-organisms from Rainwater-Ice, and Hail. By R. L. Mappox, M.D., Hon. F.R.MS., &. (Read 10th May, 1882.)
Tue study of the minute organisms belonging to the Schizophytes is one of special interest, for they touch the final history of all living beings, and very possibly hasten, if they do not actually cause, premature death. The researches within late years by very able microscopists and members of the medical profession have been numerous, though far from exhaustive. They embrace almost every field of inquiry, as the valuable Summary in the pages of the Journal of the Society so well attests; hence, some one may have preceded me in similar observations, as ice, hail, snow, rain, and dew have each been often examined; I am not aware, however, that the points I have to mention have been specially noticed; and I therefore trust they may not be wholly devoid of interest, even in their incompleteness.
The winter of 1880-81 was of considerable severity from the ex- treme cold, which if already forgotten, allow me to recall to memory, by stating the fact that at my residence, one day whilst at dinner, with a good fire in the room, water when poured into a tumbler immediately became a mass of beautiful ice-crystals. The out-of- door temperature for several days was such, that the rain-water in the open garden rain-water butt was frozen to the depth of more than 12 inches. When the thaw occurred, I placed a large block of the ice, after well draining, in a clean new pan, and removed it into the house, set it in a fireless room, and covered it carefully from the dust.. Three days later I noticed a thin scum extending over the entire surface of the water in the butt, and at once put some on a slide and examined it with the Microscope. It was found to be a mass of micro-organisms lying in a pellicle inter- mixed with particles of soot, dust, and a few minute oily-looking
Ser. 2.—Vor, II. 2H
450 Transactions of the Society.
globules. The organisms differed from any I have ever noticed before or seen figured in any papers treating on Bacteria. Slides were prepared, some without staining the objects, others by staining with aniline blue, and much later on were photographed, using a +-inch objective and artificial lamp-light. The exposure upon the (commercially so called) “instantaneous” gelatino-bromide plates varied from four to five minutes. The negatives, from deficiency in actinic power of the light employed, were too thin to furnish fair paper prints; hence they were copied upon wet collodion into positives, and these by the same procedure into denser negatives with some enlargement compared with the originals.
The micro-organisms in the pellicle, as seen under the Micro- Scope, appeared as minute rods or joints very irregularly shaped, and most of them larger at one end than the other, being either club-shaped or like the handle of a pistol, possibly due to the formation of a spore at that end, though this is doubted by some, for many had lying upon or near to the thick end a round or oval body, as if it had escaped from the adjacent rod. Some of the little bodies tapered gradually from the thick end. Where the placing of the pellicle on the thin cover-glass had not much disturbed its condition, the organisms were seen to lie very generally side by side, though not evenly, and in more or less slightly curved lines, as if the growth had been in a longitudinal direction upon a gentle curve, yet not giving rise to the sharper curve seen in many of the rods forming the mass. Amongst the numerous figures given in the ‘Annuaire de l’Observatoire de Montsouris,’ for the last three years, by M. Miquel, of the various micro-organisms he has found in the air by daily systematic observation, I have not noticed one similar to the one described. Besides these organisms there were a few small bodies in the pellicle, looking like ordinary bacteria and micrococci; but the general mass in the scum con- sisted of the large forms. ‘Their size varied considerably, the large ranging from the 75, to 45 of an inch, and the small of the same kind, to little more than half this length. Whether these bodies should be placed in the Schizophytes as Bacteria or Bacilli, I was doubtful, as more experienced observers than myself differed in opinion. No movement was seen in those freed from the broken edge of the pellicle. The difference in shape from the ordinary Bacilli rods might have been due to hindrance in their development from the previous severe cold, though if confirmed in future observations, it may be of a specific character.
The block of ice removed to the pan, furnished on the third day a pellicle which was much thinner, but contained exactly similar rods. There was considerably less contamination. ‘The same was examined at different periods, and after remaining undisturbed for more than thirteen months showed the rods to differ but little from
On Micro-organisms from Ice, &e. By Dr. Maddox. 451
the original ones ; being rather straighter, the club or pistol-handle shape still very evident, and the rods in somewhat more regular position. From the result of my rough cultivation experiments I am inclined to regard them as Bacilli. A few cultivations were attempted with the pellicle from the water-butt, also from the pan. For instance, I tried to cultivate them in sterilized (i.e. by boiling) normal urine, in sterilized infusion of Liebig extract of meat, upon cold boiled potatoes and the white of hard-boiled egg, without increased temperature beyond that of a fireless room, but with no positive success. Yet eight months later a speck taken from the pellicle, removed with some of the water from the butt at the time of the original observation, carefully kept covered and un- disturbed, and which contained the club-shaped rods in abundance, when placed on sterilized gelatine jelly prepared with infusion of Liebig extract of meat, showed ready growth in the rods, some to more than twice their original length, others multiplying into short joints. In the long ones the characteristic irregularity of outline was apparent in very many. The growth from two minute specks placed one at each end on a layer of the jelly, poured on a scrupu- lously clean slide, soon covered in length the intervening distance of an inch. Curiously, they were more or less arranged in circular groups, the centre being often occupied with a beautiful rosette of some salt crystal, though the individual rods were without regular arrangement, the short rods crossing each other in all directions. After such an interval it would be hazardous to say they were all derived from the club-shaped rods. What I wish to note is, that they grew into longer ones, so to establish their claim to be placed amongst the Bacilli. Later still, in the month of April this year, some of the same pellicle was sown on peptonized gelatine jelly without any evidence of the growth of the rods, and at the same date some placed on hard-boiled white of egg offered no change discernible, though in both cases there were very many minute organisms, as bacteria and micrococci, in Brownian move- ment. I may note that Mr. M. A. Veeder, U.S.A., found that various infusoria, conferve, &c., in the sediment of the clearest parts of blocks of ice from stagnant water of ponds and canals, would revive when melted, and considers such ice doubtful for drinking purposes.
I will now pass to some remarks on the micro-organisms found in melted freshly-fallen hail.
A rather heavy hailstorm happening on the 25th of last March, I took the opportunity to collect some of the hail for ex- amination while the storm continued, by dipping a perfectly clean tumbler into a drifted heap lodged in one corner of the window-ledge, without touching anything else ; immediately cover- ing the tumbler with a clean plate of glass, and msn be hail
2H 2
452 ‘Transactions of the Society.
to melt in a room without a fire. On the second day a faint scum was visible on the surface in patches, enveloping grey, soot-like particles. Some of this pellicle seen under the Microscope showed very pale, motionless organisms lyimg in it, resembling rather elongated micrococci. ‘The water was left further undisturbed for another day, but furnished no appreciable difference except greater distinctness of the imbedded organisms. Some of the pellicle was stained with aniline blue, and mounted in acetate of potash solution without having been dried. Whether from want of refractive differentiation between the objects and mounting medium, or from the acetate of potash acting upon the pellicle, the outlines of the minute organisms were indistinct ; consequently a different method was adopted, which seemed to offer advantages. A speck of the pellicle was placed, with as little disturbance as possible, in a droplet of distilled water on the cover-glass, then, as recommended by different observers, dried over a flame, in this case very slowly. Afterwards it was covered with the following staiming fluid and protected from the dust : —
Bismarck or aniline brown (of German make), 4 grains; citric acid, 16 grains; distilled water, 200 minims; boiled in a test-tube, cooled, filtered, reboiled, and a trace of carbolic acid added.
After being covered with the staining medium for an hour it was washed with distilled water by tipping off the fluid, draining closely on blotting-paper, repeating this until the water was colourless, then drying again by gentle heat and mounting the cover dry.
Deion I tried the aniline brown without the citric acid, but the addition of the latter appeared to facilitate the washing by increasing the solubility of the colouring agent without lessen- ing the staining qualities.
Great care was required if the specimens were washed with the cover on the slide, for the least displacement caused the pellicle with its organisms to roll up into continuous lines.
I am not prepared to say that the method of drying does not slightly shrink the objects. I fear it does, though I do not think more than osmic acid, as the substance enveloping the organisms appears indistinctly afterwards. The minute bodies found in the melted hail differed most completely from those of the frozen rain-water. In parts where but little disturbance of the pellicle occurred upon removal for examination, the organisms were seen lying very irregularly near to each other, whilst in what appeared to be a second pellicle formed just beneath the outer one, they occurred mostly in rows, and are often at rather an acute angle with one another. In size they differed, doubtless owing to being in various stages of growth and fission.
On Micro-organisms from Ice, dc. By Dr. Maddox, 4538
The average size is from the szioo to the rstoo of an inch in length ; some looked round, others like elongated micrococci, and when fission was about to occur very like ordinary bacteria. As they were when free motionless, I felt inclined to suppose them to be micrococci, but from some cultivation experiments I believe they must be termed bacteria.
Thus a speck of the pellicle was placed on freshly boiled white of egg, and kept carefully covered and turned down without touch- ing anything except by the broken shell edge. The second day, about thirty-six hours after the inoculation, on removing a minute portion and diluting it with distilled water, it presented an in- credible crowd of bacteria in rapid motion, resembling closely, if not actually, Bactertwm termo. On the sixth day the white of egg, at the spot of inoculation and for some distance beyond, pre- sented a beautiful pale canary-yellow colour, and on the eleventh day a bright deep rose-coloured spot also appeared, very closely to the seat of puncture, consisting of motionless micrococci. This has been successfully cultivated ‘through several generations on the same medium.
A portion of the original pellicle placed on peptonized gela- tine jelly on the thin cover, and this placed over a tin cell cemented to an ordinary slide, ‘the surface of the tin circle being smeared with vaseline (as recommended, I believe, by an American microscopist), except at two small opposite points, and then kept at the temperature of about 58° F., had on the second day so softened the gelatine by the changes induced in it, that the spot of inoculation was quite fluid, teeming with minute organisms in most rapid motion ; hence, as several inoculations were made, and with like results, I conclude that chiefly bacteria and only few micrococci existed in the hail in a quiescent or resting stage, and when supplied with proper nutriment and more favourable condi- tions, the organisms, suited to the circumstances, quickly turned from the quiescent state to one of the greatest activity. Of course I do not pretend there may not have been different varieties in the hail, for the organisms of rain-water have been found to determine butyric, lactic, ammoniacal and putrefactive fermentation; but what appears to me probable is, that one if not more amongst the organisms supported the temperature, whatever that might have been, that determined the formation of hail, remaining in an almost quiescent state, for I believe the Bacteria have their resting stage, and that the more advantageous conditions of nutriment and temperature speedily determined activity. The general mass of the jelly remained free from visible change. Before actual fluidity of the material occurred, close to the inoculated spot, numerous small, round, grey, finely granular, ascococcus-looking
454 Transactions of the Society.
patches made their appearance, and gradually coalescing, joined the edge of the inoculation. Of their nature I can say nothing definite. How they came there is rather puzzling, seeing none formed in other parts of the jelly.
At the same time, and in a similar manner, the same nutrient medium was inoculated with a speck of the old pellicle from the ice in the pan: the club-shaped rods did not, at this date and in this medium, undergo any visible change ; but some of the minute organisms showed development, though not to any great degree, only exhibiting Brownian movement, whilst some of the same pellicle placed on the boiled white of egg at the same time as the former experiment with the pellicle from the hail, furnished on the second day minute organisms which, when seen in a droplet of distilled water, were not very active; but the club-shaped rods, if they multi- plied, did so to an indiscernible extent. ‘There was no chromo- genous change at the point of inoculation, as with the pellicle from hail.
The minute organisms found in the melted hail-water scum, were no doubt derived from the rain-drops congealing round the air-borne dust-particles to which they were adherent, and after- wards slowly multiplied afresh on the surface of the melted hail. Some have doubted whether bacteria form part of the atmospheric dust; but the very careful experiments and cultures of M. Miquel, at the Montsouris Observatory, tend to prove that such bodies are suspended in the air and to be constantly found in rain, hail, and snow. Numerous figures are given. ‘To avoid contamination in culture experiments, when objects are only for a short time exposed to unfiltered air, is a great source of difficulty. M. Miquel remarks in the ‘ Annuaire,’ published this year, that snow, usually regarded as the great air-purifier, is not so in reality, for although it largely attracts the bacteria it meets with in its passage, it does not fix them like moistened earth; as a sudden squall cutting into the snow will often again bear them aloft. January and February have furnished him with the minima; October and November with the maxima in the gatherings. Cold he places the first, and extreme dryness the second agency in the destruction of atmo- spheric bacteria. Rainfall much lessens their number, whilst this again rises upon the succeeding dryness. He finds them ten times more numerous in the centre of Paris than in the country, for the same volume of air, and he gives the proportional numbers as, micrococci 93, bacilli 5, bacteria 2, for the first, and micrococci 79, bacilli 14, bacteria 7, for the second. He also furnishes the mean for the different months. The micrococci are pretty con- stant, the bacilli highest in April, May, July, and August, and lowest in November, January, and June; the bacteria nil in January, February, and June, and highest in the month of May.
On Micro-organisms from Ice, dc. By Dr. Maddox. 455
The difficulty is to find a suitable medium for nourishing or rejuvenating all the aerial germs that have been gathered by the aspirator.
The great extremes of heat and cold to which the spores of many of the Schizophytes have been exposed without loss of vitality is a point of much interest. The Rey. Mr. Dallinger, in his careful experiments, found the death-points in dry heat, for the mature monads that he had studied, to range from 138° F. to 142° F., but their spores supported for five to ten minutes 250° to 300° F.; whilst the same heated in fluid were destroyed at 212° to 268° F. M. Van Tieghem found some micrococci and bacilli to flourish at 74° C. M. Miquel cultivated one form from the Seine at 70° C., which died when the temperature was raised to 72° C. Professor Frisch finds that the bacteria seen in diphtheritic exudation and in puerperal fever resist a minus temperature of 87°5° C. without destruction, and the bacilli spores to resist extremes of cold better than the rods. M. Miquel states that a particular Bacteriwm found in snow resisted a temperature of 26° to 30° C. below freezing for three hours, and for more than twenty days a mean temperature below zero of 2°5° C. The enumera- tion of such experiments might be greatly multiplied.
Drs. Cohn and Mendelsohn state that it required a powerful galvanic battery current of five elements to destroy the vitality of the bacteria they experimented upon.
Not to quote more largely, it seems quite incomprehensible that such minute organisms should be able to resist such extremes of temperature, and that the so-called mucous, gelatinous, albu- minoid, cellulose, or by whatever name it may pass, covering, which is permeable to fluids, should be able to defend the living contents against such extraordinary variations of heat and cold. Here, under the hand of most careful experimenters, the reasonable- ness of previous doubt must give place and credence to the senses. Can it be that the envelope that surrounds the organism normally, when subjected to dry heat, dries so entirely and rapidly as to prevent the entire loss of moisture from within, or that the encap- sulation, so to speak, is so perfect, that there is no room for the generation of high-pressure steam, and that under moist heat the coagulation is so effective that it shrinks the outer material so closely upon the contents, that steam cannot be generated except under rupture? Or can the rapid chemical changes they can effect, suffice to continue their vitality under such abnormal conditions ?
We may largely theorize, though I fear only to record our ignorance, when we attempt to limit the manifestations of life by predeterminate lines, derived from the study of higher organisms, though amongst these there are some, as the Aphides, stated to
456 Transactions of the Society.
resist extreme cold, and in the case of seeds and chestnuts they are said to have survived the exposure to the very low temperature of —100° C., and very lately in experiments by Messrs. de Candolle and Pictet the refrigeration was carried to — 80° C., the seeds germinating afterwards. I think experiments have also been made on hybernating animals, but I do not remember the exact temperature destructive of life. The minuteness, however, of the Bacteria almost forbids comparison with the other objects.
Such details I fear must be sadly wearying to those who take no special interest in the study of these micro-organisms, and to such I offer every apology. Nevertheless, I would ask them to try and estimate carefully the value of the study of these ubiquitous objects. ‘They set up minute changes in some of the articles of our dietary as either invite or repel the organs of smell and taste. The numerous varieties found by M. Duclaux in the imperfect making of Cantal cheese, at once point to a large field of inquiry among the articles that are in our daily diet. They play a vast role as the grand scavengers in the silent destruction of lifeless forms and are thus beneficent agents; they are the companions of our life and accompany, if they do not originate, many depressing and fatal diseases, multiplying so rapidly in cases of lowered vitality of their host that they kill by their numbers, or perhaps by depriving the nutrient fiuid of part of its oxygen, though this, as pointed out by Mr. Dowdeswell in his excellent article upon Septiczemia,* seems, in the smaller forms at least, improbable. ‘The chemical changes induced by their own require- ments may furnish noxious matters detrimental to the life of the higher organism—and harmless forms under new conditions may perhaps acquire such virulent properties, that in the state of spores the minutest quantity suffices when inoculated into the connective tissue of a healthy animal, if such have not acquired previous immunity, to cause severe illness if not certain death. Their importance, as affecting, on a vast scale, the life of man and of animals, invests them at least with the symbol of respect.
It is only by cultivation that we can hope to distinguish the living from the lifeless, for may we not have before us in such as are gathered from the air, some that are dead, and some of what Dr. Phipson calls “ fossil forms.” Morphologically their resem- blances may be so great that their differences are to our powers other- wise indistinguishable. Possibly some may be inert when cultivated in one fluid, and highly poisonous in another—as in living bodies.
* Quart. Journ. Micr. Sci., xxii. (1882) p
+ M. Miquel found by the statistics of ine ae that occurred last year at Paris, that there were nine rises which closely corresponded each to a rise in the number of Schizophytes found in the air. He merely points out the interesting coincidence.
On Micro-organisms from Ice, &e. By Dr. Maddox. 457
The necessity for a certain amount of the poisonous material to be introduced or acquired in the system to produce on the one hand immunity, or on the other hand fatal effects,—the alteration some undergo by exposure to air,—the re-acquirement of highly virulent properties after having had them lessened by culture, may, perhaps, point to the very variable results exhibited in contagious maladies, and malarial fevers, under similar exposures; some receiving the contagium, so to speak, at its first offer, others resisting for lengthened periods.
In the case of malarial fevers there are some points that furnish material for future study. I will mention an instructive case that came under my notice many years since. In the neighbourhood of Constantinople, and especially at the Dardanelles, malaria was endemic. Asswming malarial fever to be consequent upon the introduction into the system of the Bacillus malarix of Klebs and Tomassi-Crudelli, this point for inquiry arose. A sailor had had at one of the ports in the East Indies a first and severe attack of intermittent fever, from which he speedily recovered, and remained free from any recurrence for thirteen years, although visiting various localities where such fevers were common ; yet the same night that his vessel anchored, during the day, in the Golden Horn, he was seized with a severe attack of malarial fever, which necessitated his entry into the hospital. None of the officers or crew suffered similarly, though remaining many days at anchor. Are we to suppose the germs of the former malady remained quiescent in the system for the period of thirteen years, and that a few hours in a suitable locality sufficed to set them into activity and develope a return of the ague; or was he an individual very susceptible to malaria? I scarcely think so, as he was free at other ports where the malady was common. Again, should the second attack be supposed as unrelated to the first, under the assumption that he in some way imbibed the malaria in passing the Dardanelles, and that the incubation took three or four days to develop itself, or was it that out of all the places he had visited in the course of his voyages for thirteen years, this locality was the only one to furnish the necessary conditions for a return of the original malady, he being previously in good health ?
In the malignant form, in the neighbourhood of the Darda- nelles, I have known individuals die in the cold stage within sixteen hours. Had such imbibed a really toxic quantity of the malarial poison—I am expressly assuming the correctness of the Bacillus malariz theory, which Dr. Sternberg, U.S.A., finds reason to doubt —and did the organisms multiply in such a short period throughout the system or in some vital organ as to thus speedily terminate life without any reaction, under every effort that time permitted ?
Mr. E. L. Moss, Staff-Surgeon R.N., found, after forty-eight
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hours, by ingeniously contrived experiments, organisms in the blood drawn from intermittent fever patients which he could not find in the fresh blood. It is questionable whether they were the same as the Bacillus malariz.
Dr. Marchiafava contends for the correctness of the statements of Klebs and Tomassi-Crudelli, for he finds the blood of all parts of the body, in those stricken with malarial fever, to contain in the initiative or cold stage both barren and spore-bearing rods, and in the hot or fever stage, only free spores.
The cyclical course of various infectious diseases is attributed by Dr. Wernich and Professor Salkowski, from their careful experi- ments, to the destruction of the micro-organisms in the living body by their own products, i.e. they are destroyed by their own excreta.
What the term of life may be for the spores of these lowly forms awaits inquiry. The germs of Bacillus anthracis are said by M. Pasteur to have survived a period of twelve years, but how much longer, lies in the investigations of the future.
The medical digression has been purposely made to try and engage some of the waste microscopical energy of the members of this Society by showing that complex phenomena attributed to the action of such micro-organisms yet wait for intelligible and satisfactory answers. There is one hint I would throw out_to those who need the stimulus of patient work, viz. to follow up the researches of M. Chappuis, by watching the effect of ozone upon the life of the Schizophytes. Such an inquiry may lend light to the obscurity that now veils some of the depressing catarrhal epidemics, such as influenza, &c.
Although much has already been accomplished, much has to be repeated. As yet we only touch the edge of this vast field for research. In it stands a complex problem for those to solve who have the time and patience to compete for even a fractional part. Fortunately encouragement comes from the important ex- periments now made in other countries, in the form of “ pre- ventive inoculation,” from which, already, highly beneficial results have been achieved, conservative both to life and to the pocket. May we not apply to ourselves what has been so ably said by Dr. Burdon Sanderson in his recent Lectures upon Inflammation ? “ We are all of us, old and young, too apt to forget how slow and gradual is the process by which we come to a right understanding of objective facts. Let us be prepared to give equal credit to the past and the present, accepting what is new without losing sight of, much less rejecting, what is old.”
[Since the foregoing was written, that indefatigable observer Dr. Koch has discovered another of the Bacteria which he, followed by Dr. Baumgarten, considers as the cause of tuberculosis—a disease
On Micro-organisms from Ice, de. By Dr. Maddox. 459
which is responsible for about one-seventh, if not more, of the deaths of our population. Dare we hope that further ex- perimental research may ultimately arrive at some method of diminishing this frightful annual loss? Shall we get a clearer insight into what we term the law of heredity? Supposing infection ab utero, has it no limiting period of incubation? must all ages bend to its presence? J am not aware whether the organisms found in fowl cholera have as yet been discovered in the newly laid egg. The answer can only come from careful experimental inquiry. In it lies the hope of discovering the means of immunity, and I trust that, in spite of hasty and prejudiced legislation, such researches may yet be made in this country, as will conduce, not alone in this, but in other maladies, to the future welfare of both man and beast, so that we may say in the words of the poet :— “?Tis worth a wise man’s best of life, *Tis worth a thousand years of strife,
If thou canst lessen, but by one, The countless ills beneath the sun.”’]
460 Transactions of the Society.
XI.—The Relation of Aperture and Power in the Microscope (continued).*
By Professor Apps, Hon. F'.R.MLS. (Read 14th June, 1882.) II.—The Rational Balance of Aperture and Power.
The discussion of Part IJ. relates to one and the same matter, viz. that from all points of view which come under consideration in the use of the Microscope, a certain proportion of aperture to power is the necessary basis of perfect performance.
The question we have now to consider is: whether it is possible to arrive at a more definite determination of that propor- tion than is furnished by the preceding somewhat general dis- cussion of the question of wide and narrow apertures, and in particular, whether that can be done in such a way as to establish a rational standard for the practical construction of the Microscope. So far as I know, this matter has not yet been the subject of any kind of regular discussion, though it will be admitted, I presume, by every microscopist to be one of great practical importance. I have now directed my attention to it for more than ten years, not purely from theoretical points of view only, but by means of a long series of practical trials in which I had the advantage of the co-operation of Dr. C. Zeiss, of Jena, and I propose therefore to point out here the principles which, in my opinion, furnish an approximate standard for determining the proper balance of aperture and power in the Microscope.
For this, two distinct questions must be treated separately.
First, the relation of aperture to power must be considered in regard to the entire Microscope and we must ascertain what amplification of the ultimate image of the Microscope is useful, or necessary, for every given aperture, and conversely, what aper- ture is required for the proper utilization of a given amplification. If the subject admits of a scientific discussion at all, it must be possible to indicate the proper relation of aperture and amplifica- tion without having regard to the particular manner in which a given amplification is obtained by the co-operation of objective and eye-piece, provided, of course, that the amplification is obtained with the best possible quality of the image.
The second question is, what division of the entire power of the Microscope between the objective and ocular will fulfil the condition of a perfect image under a given amplification. This relates essentially to the practical aim of the discussion—the determination of the focal length of the objective which is required for the utilization of a given aperture.
* The paper (received 11th April) is written by Professor Abbe in English.
The Relation of Aperture and Power. By Prof. Abbe. 461
i. Relation of Aperture to Power in regard to the entire Microscope.
. 1. The first question may be dealt with under these two heads :—(a) What are the smallest dimensions of microscopical detail which are within the reach of any given aperture ? (b) What visual angle is required for the distinct recognition of details of given dimensions? If these can be answered in a reliable manner, the first question will have been disposed of.
The smallest dimensions which are within the reach of a given aperture are indicated with sufficient accuracy by taking the limit of the resolving or separating power of that aperture for periodic or regular structures, i.e. the minimum distance apart at which given elements can be delineated separately with the aperture in question. The numerical expression of that minimum distance is
A i eresh ee
where a denotes the numerical aperture and X the wave-length of light ; a fair average is obtained for the latter element (with observations with the eye and white light), by taking X = 0°55 w = 0°00055 mm.; i.e. the wave-length of green rays between the lines D and H, very near to the point of maximum visual intensity in the diffraction spectrum.
Though this expression applies in strictness only to the visi- bility of periodic structures composed of regularly arranged elements, it may be taken as an approximate measure of delinea- ting power in general, i.e. in regard to structures of every composition. My theoretical investigations and experiments show that with objects of every shape and arrangement, the micro- scopical image will not present any indications of structure, the dimensions of which are perceptibly below the value of 6, given (for any aperture) by the above formula. Prominences of any shape on the outline of a coarser object, for example, will disappear more and more as their dimensions approach the value of 6 for the aperture in use. Isolated elements of triangular, or quadratic, or rectangular figure will look more and more alike (becoming more and more circular or elliptical in form), as they diminish in size to the value of 6.* The loss of diffracted light attendant upon the limitation of the pencils by the lens-opening, changes or obliterates those details which are beyond the limit of the resolving power. Consequently the microscopical image of an object of any composition whatever, will always be disstmdlar to the object to the same extent; and the limit of resolving power therefore indicates the limit of simalar or correct delineation generally.
* I have verified these theoretical inferences, for small apertures, by many experiments, with objects of very different nature.
462 Transactions of the Society.
Hence every aperture is fully utilized when the amplification of the entire Microscope is sufficient for a distinct and convenient observation of details corresponding to the value of 6. Lower amplifications would not exhaust the aperture, because indications of real structure which exist in the image, would remain hidden from the eye. Higher amplifications, on the other hand, will not promote the recognition of the objects, because all the indications of minuter scale which they might perhaps display, do not exist in the objects, but belong to the image only—they are simply modifications of the image due to the aperture in use. Such higher powers would therefore afford nothing more than an exaggeration of those features of the image which are not conformable to the real nature of the object.
We have now therefore reduced the problem under consider- ation to the single question: What amplification is necessary and sufficient in order to display the 6 of every aperture, under that visual angle which is required for distinct vision ?
The facts of observation which are within the reach of every microscopist, afford all necessary data for an approximate determi- nation of this amplification. The striation of an ordinary specimen of Pl. angulatum becomes visible to a very sharp-sighted eye under an amplification of 150 diameters. As the closeness of the lines is about 0°5 w (50,000 to the inch) they are thus recognized under a visual angle not much exceeding 1’ of are. But dastenct and convenient observation for an average eye will in any case require a much higher power; how much higher, will of course vary with different individuals. I am, however, sure to leave sufficient latitude for personal diversities in assigning 300 and 600 diameters as the limits of useful amplification for details of these dimensions. In observing the diatom, no one, I presume, will deny the advantage of increasing the power if it 1s below 300; and on the other hand, no one will admit any further advantage in going beyond 600, provided the observation is made with an aperture not exceeding 0:6, which shows the striz, but nothing more.*
It may be inferred from this example, in accordance with many similar facts, that satisfactory observation requires that the smallest detail of the microscopical image shall be displayed under a visual angle of not less than 2' and not more than 4’, approxi- mately ; angles which correspond very nearly to the amplifications 300 and 600 for dimensions of 0°95 p.
This admitted, we obtain at once the number of diameters which are required for properly utilizing any given aperture. If a dimension 6 is to be displayed under a visual angle of v minutes of
* Much higher powers may of course be utilized in the observation of Pl. angulatum with objectives of wide aperture. In this case, however, the image contains indications of form upon the markings of much minuter dimensions.
The Relation of Aperture and Power. By Prof. Abbe. 463
arc, the necessary amplification, N, for a distance of 250 mm. or 10 inches (1' being = 1 : 8438) is 250 v
~ 3438 | 5”
and substituting for 6 its equivalent in terms of the aperture (=) a
we obtain the general formula :—
250 2av ae oe or, if X is taken = 0°00055, N = 264:'5 av,
By introducing into this formula v = 2' and v = 4 respectively we obtain the figures of useful amplification for a series of different apertures. as shown in Table I.—useful, that is, so far as delineating power is concerned, putting aside for the moment any question as to the dlumination of the object, which, as explained hereafter, allows of somewhat greater apertures.
TABLE I. 5, N, Amplification for obtaining a Aperture, Aperture-Angle Measure of the Visual Angle of (air). least attainable Detail. ey v=! = Ie
0°05 a°7 5°50 26 53 0°10 11°5 2°75 53 106 0°15 17°2 1°83 79 159 0°20 23°0 1:37 106 212 0°25 29° 0 1:10 132 265 0°30 35°0 0:92 159 317 0°35 41°1 0°79 185 370 0°40 47°2 0°69 212 423 0°45 03'°5 0:61 238 476 0°50 60:0 0°55 264 529 0°55 66°7 0°50 291 082 0°60 (oe 0°46 317 635 0°65 81°1 0:42 344 688 0°70 88°8 0°39 370 TAX 0°75 97°3 0:37 397 794 0°80 106°3 0°34 423 846 0°85 116°4 0°32 450 899 0:90 128°3 0°31 476 952 S95) 143°6 0:29 5038 1005 1:00 180°0 0°27 529 1058 1:05 of 0:26 555 1111 1:10 0:25 582 1164 1°15 0°24 608 1217 1:20 0°23 635 1270 1°25 0°22 661 1323 1°30 0:21 688 1375 1°35 0:20 714 1428 1-40 0.19 (Ea) 1481 1:45 0°18 767 1534 1:50 0°18 793 1587
464 Transactions of the Socvety.
Conversely we can obtain the aperture a, which is sufficient for the utilization of a given power of N diameters, provided a visual angle v' is required for the least detail within the reach of that aperture. This is given by the formula
) 4, ap Sees 264°5 *
Table II. shows the values of a corresponding to different amplifications under the supposition of a visual angle vy = 2'; it exhibits, therefore, the maavmum aperture which can be admitted as useful for any given power under the above assumptions. The assumption of any other visual angle as necessary for distinct vision of the least detail, would change a in the inverse pro- portion of v, so that for v = 1' we should have twice the figures of a given in the second column of the table, and for v = 4’ one-half.
Tas_eE II.
a, N, Aperture for Amplification | @ Visual Angle of Aperture-Angle for 250 mm. the least detail, (air). De
fe)
10 0:019 2°2 20 0-038 4-4 30 0°057 6°5 40 0-076 8:7 50 0-095 10:9 75 0:°142 16°3 100 0-189 21°8 150 0-284 33°0 200 0°378 44°4 250 0-473 56°95 300 0°567 Goat 350 0° 662 82-9 400 0°756 98°2 450 0°851 116°7 900 0-945 141°8 600 1:134 700 1°323 800 1°512 900 1:701 1000 1°890
i
Though these figures cannot of course pretend to be more than an approximation to the actual requirements under various given conditions, yet they will indicate with sufficient accuracy the limits of useful power; in that the delineating power of any given aperture cannot be fully utilized when the number of diameters (obtained with a really good quality of the image) is much below the minimum figures of the table; and that, on the other
The Relation of Aperture and Power. By Prof. Abbe. 465
hand, we shall have an empty amplification, which does not improve the representation of the objects, if the power should go much beyond the maximum figure.
The salient fact suggested by the two tables is the relatively low figures of amplification which are sufficient for very wide—in particular for the widest—apertures; and, conversely, the small apertures which are sufficient for the low powers of the Microscope. I do not, of course, intend to assert that, under particular cir- cumstances and for particular purposes, much higher figures of amplification than are shown in the tables may not be very useful or even necessary ; as, for instance, for counting, measuring, draw- ing, &e. What I wish to convey is, that in the present state of the Microscope they are not required and are not even advantageous, for research, i.e. for the proper recognition of the objects. A visual angle, for the minutest elements of a microscopical image, of 2', or at all events of 4’ (which is about the eighth part of the moon’s apparent diameter), is certainly quite sufficient for distinct observation. If indications of shape or arrangement should be found in the image, which are too minute for the powers given above, they must be at any rate of minuter dimensions than the values of 6 assigned by the first table. Indications of that kind— if such there be—have no true relation to the objects, but are attributes of the image only—mere optical phenomena, dependent upon the limitation of the delineating pencils by the lens-opening.
Apart from all theory and experimental demonstration in sup- port of the principles in question, the practical experience of micro- scopists has sufficiently established that there 23 a limit to the performance of the Microscope, and one depending on the aperture of the objectives in the manner pointed out above. No kind of microscopical object can possibly afford in any respect more favourable conditions for the recognition of minutest details than those very expressive (and at the same time very simple and regular) structures of the silica skeleton of diatoms. But even with this kind of object not one trustworthy observation is on record in favour of the assumption that any given aperture, be it either 0°3 or 1-40, could reach a finer detail than is assigned by the table above, whilst there are many indubitable proofs that these theoretical limits may be as closely reached as can be expected, having regard to the difficulty of a strict determination of the actual circumstances of observation.
The low figures of amplification suggested above, even for the widest attainable apertures—low in face of the views of many microscopists—are an unavoidable inference from the principle under consideration. In support of this inference I may, however, appeal to the evidence of many experienced naturalists who have done valuable work in lines of research dealing with the most
Ser. 2.—Vot. II. dae |
466 Transactions of the Society.
minute and delicate objects, and who agree that all real increase of our knowledge, even in these branches, has been originally obtained, or at least could have been as well obtained, by powers not much exceeding 1000-1200, whatever kind of lenses may be in question.
2. I cannot, however, restrict myself to the suggestion that excess of power, in proportion to the aperture in use, is simply of no advantage for the recognition of microscopical objects, but I must go further still, and express the opinion that excessive power is, or at least may be, a positive obstacle to correct recognition, because it will unavoidably lead the observer to take mere optical pheno- mena of the images for real attributes of the objects. ‘The following considerations will justify this view.
If we observe a frustule of Pl. angulatum with the small aper- ture of about 0-6, in which case one set of lines only is exhibited at once, we may obtain a well-defined image of these lines under a power of 1000 diameters, or even more, provided a relatively short focal length of the objective and a moderate eye-piece are applied, and the illumination is effected by a very narrow beam of intense light. This power apparently displays much more than a lower power of 350 or 400 diameters with the same aperture. We see the striz as broad ridges or grooves widely separated from one another, and we recognize a distinct proportion between the breadth of these apparent ridges and their interspaces, which is 1 : 1 very approxi- mately ; whilst with 300 diameters we only catch just the fact of a striation, and nothing more. In this case now, we know that all details which are given by the 1000 diameters are mere optical illusions, because we are able to control and correct the indica- tions furnished by that power with the low aperture, by the image presented by an equal power, but having an aperture of 1:2. But if it had happened that a system of wider aperture than 0°6 had not hitherto been made, microscopists would cer- tainly have believed in the existence of ridges and grooves of equal breadth on the scale of Pl. angulatum. In this example it is unquestionable that the image obtained with an aperture of 0°6 under 300 diameters is less far from the truth than the image with the same aperture under 1000 diameters. The indeterminate striation is an indication of real structure, inasmuch as there are equidistant rows of elements in the diatom, which must appear as strie as long as the elements themselves remain occult; the exhibition of these rows as determinate ridges and interspaces with a distinct relation of breadth is a positive adulteration of the image of the structure.
What holds good for an aperture of 0°6 must also hold good for every larger aperture relatively. I have before me Dr. Wood- ward’s magnificent photographs of Amphiplewra pellucida, Pl. angu-
The Relation of Aperture and Power. By Prof. Abbe. 467
latwm, and other diatoms, taken with the best wide-angled lenses under amplifications of about 3000 and more diameters. Now the Amphipleura of these photographs, taken with apertures of 1:2-1°3, is the true equivalent of the Pl. angulatum of 1000 diameters with only 0°6 aperture. It shows the same determinate and energetic striation with equally broad ribs and interspaces, which are always seen when the closeness of the structural elements is not far from the limit of separation for the aperture in use. Theory and experiment show that these details of the image have no relation to the real composition of the object, that they exhibit nothing more than fypical pictures of rows of elements of any shape and magnitude whatever, when their closeness approaches the value of 65 corresponding to the aper- ture. It would be contrary to all analogy to expect that in Amphipleura alone we should have real bands or ridges, and not, as in other diatoms, distinct elements of double periodic arrangement with different closeness in different directions. This admitted, the enhanced expressiveness and determinateness of the image with the higher power is just the opposite of enhanced recognition, because the eye is caught by features which are entirely foreign to the object. If I wanted to show to any one what the Microscope has really revealed of the structure of diatoms, I should request him to inspect the said photographs at a distance of three or four feet, in order to restore the smaller visual angle corresponding to an amplification of about 1000 diameters. What he is able to recognize under these circumstances are the vestiges of true structure—indefinite, perhaps, but not falsified ; what he sees move under greater visual angle is nothing but the display of dissimilarity of object and image arising from the lack of aperture. The 3000 or 4000 diameters could improve the recognition of the real structure, only if they were obtained by apertures of 3°0 or 4°0.*
It is by no means otherwise with the very minute objects of entirely different lines of research. If the image of a bacterium or a very delicate flagellum is exhibited under a power of 3000 diameters with more distinctness, as regards shape and magnitude, than is possible with one of 1000, the surplus will always be a surplus of mere optical dissimilarity.
The effects of excess of power in the Microscope may be illus- trated by similar facts of astronomical experience. Astronomers
* The figures of the tables should not, however, be applied directly to photographic performance, but the powers indicated for each aperture should be increased in the proportion of 0°41: 0°55 (3: 4 approximately), and the aperture corresponding to a given power diminished in the same proportion. Owing to the shorter wave-length of the rays of maximum chemical intensity, the value of 6 for every aperture is proportionately smaller in photographic than in ocular observation.
212
468 Transactions of the Society.
know very well that the most trustworthy power of a telescope is not the highest power which the instrument will bear, but that power which has a certain relation to the diameter of the objective. If they use a higher amplification than about 40 per inch of the diameter of the objective (i.e. 120 for a 3-inch, 400 for a 10-inch objective) they begin to detect diameters of stars which have no diameters. A very good 38-inch objective will, indeed, show more under a power of 300 than of 100, apparently ; just the same as with a very good wide-angled Microscope-lens in regard to 3000 and 1000 diameters. In fact, the 300 diameters of the 3-inch will reveal, with somewhat bright fixed stars, very neat and distinct disks which are invisible, or nearly invisible, under a power of 100. But these disks disappear at once, when the amplification of 300 is obtained with an objective of 9 inches diameter.* Astronomers are accustomed to apply much higher powers than 40 per inch for various purposes; but they do not apply them whenever they want to recognize the true shape and magnitude of their objects.
It is just the same in the Microscope. The greatest possible approximation of the image toa true projection of the object is not obtained by the highest powers, but by those powers which are just capable of exhibiting to the eye the least dimensions of real structure within the reach of any given aperture.
I invite the particular attention of microscopists to this subject, as it is in my opinion of great practical importance in regard to the proper use of the Microscope. For my present purpose I may confine myself to the statement that it does not belong to the rational aim of microscopical optics to enhance the amplification of the Microscope beyond those moderate figures which are sufficient for utilizing the attainable apertures; the rational aim is rather to obtain the best possible accomplishment and the most favourable conditions, for the use of these moderate amplifications.
3. So much as to the proper relation of aperture and amplifica- tion at the upper end of the scale of microscopical performance, where the question is of the largest attainable apertures and highest useful powers. In regard to the lower end of the scale, the suggestions indicated by Tables I. and II. will require some further remarks.
So far as the principle is admitted on which the computation of the tables has been based, we must consider the small apertures assigned for the lower powers of the Microscope as sufficient,
* The physical conditions of the phenomena in question are not the same in the telescope and in the Microscope, but yet very similar. In both cases the effects do not arise from deep oculars—as is often assumed—but depend only on the relation of the total amplification of the instrument to the aperture.
The Relation of Aperture and Power. By Prof. Abbe. 469
provided a visual angle of not less than 2’ is required for the smallest detail within the reach of every aperture. An increase would be a matter of necessity only if a given observer should consider a smaller visual angle, say 1', as sufficient for distinct observation. On the other hand, it is certain that a surplus of aperture is no drawback by itself, but only in regard to certain practical points, which have been spoken of in the first part of this paper. Among these are some which argue in favour of small apertures (penetration, working-distance, insensibility of the cor- rections, &c.), and one which is in favour of increased aperture (brightness of the image). The proper function of the theoretical considerations of the foregoing paragraphs cannot therefore be to establish an absolute rule, but rather to afford a proper basis for finding a rational balance between the various requirements of the practical use of the Microscope.
Regarding those in which the advantage is always on the side of the lower aperture, it will be obvious that all of them become less and less important as lower apertures and lower powers are in question. As has been pointed out in the first part, restrictions of the working distance and inconvenient sensibility of the systems (unsteadiness of the corrections for different thicknesses of the covering glass, &c.) are not met with as long as the aperture does not exceed 0°25 (about 30°) and even with somewhat greater apertures, up to 0°5, they do not occur in any very obnoxious degree. The third element, the penetration of the Microscope, has been more fully discussed on another occasion,* where it was shown that with decreasing amplification the actual penetration, i.e. the depth which is accessible to the eye with one focussing, is more and more the result of the accommodative faculty of the eye and more and more independent therefore of the aperture. With very low powers, not much exceeding 50 diameters, a normal eye has a perceptible amount of depth of vision without any regard to the aperture. The lower the power, therefore, the more liberty is left for increasing the aperture in proportion to the power without: any perceptible disadvantage in respect to the various points above mentioned.
There is, as I have said, one element in the performance of the Microscope in which a surplus of aperture will be a benefit, viz. the illuminating power, or the brightness of the image. It would, however, be a great mistake to expect that this should be without any limits or conditions, as the following considerations will show :—
So far as the illumination of the objects by transmitted light is effected with light of a given intensity, and the illuminating pencils utilize the whole aperture of the objective, the brightness
* See this Journal, i. (1881) p. 689.
470 Transactions of the Society.
of the microscopical image depends solely on the diameter of the pencils at their emergence from the ocular, and is in the direct proportion to the square of that diameter. This diameter (d) is strictly expressed by the simple formula d=20-5 (ord = 275);
if N denotes the amplification of the ultimate image for a distance of vision = J, and a the numerical aperture of the system. If we have a narrower illuminating pencil, which does not fill the whole opening of the system, the numerical aperture corresponding to the angle of the illuminating pencil must be substituted for a, instead of the full numerical aperture of the system. The diameter of the emergent pencils, and consequently the illuminating power, is entirely independent of the particular composition of the Microscope (objective, ocular, and length of the tube), and is solely determined by the aperture and the total amplification (the accidental losses of light by reflection and absorption being: dis-
regarded). By giving values to / and = we obtain from the above
formula the diameter d in millimetres. Under the assumptions made in the computation of the figures of the second column of Table IT. (i.e. % = 0°55 w and v = 2') we have a constant ratio of a: N, viz.:—
a 1 : N ~2(264°5)’
and taking 7 = 250 mm. and substituting those values in the above formula we have A 90 = eae = 0°95 mm., consequently the same diameter d for all powers, and always the same brightness of the image therefore, provided the different _ apertures are fully utilized by the incident illuminating pencils. By increasing the values of a assigned for every power N by Table II. we enlarge the diameter of the emergent pencils in the same proportion; we should, for example, have d = 1:9 mm. throughout, if the apertures—so far as this is. possible—were in- creased in the ratio of 1 : 2, which would correspond to the assump- tion of a visual angle » = I’ for the least accessible detail. It is obvious, however, that larger apertures can be of advantage only so long as the value of d does not exceed the diameter of the pupil of the eye under the actual conditions of microscopical observation; for if this should happen, the iris of the observer must stop-off the marginal part of the lens-opening exactly in the same way as if a diaphragm were placed on the objective.
The Relation of Aperture and Power. By Prof. Abbe. 471
Moreover, in microscopical observation—except under very faint illumination—the iris of a sound eye always contracts to a rela- tively narrow diameter, generally not more than 2 to 2°5 mm. Whilst, therefore, so far as delineating power alone is concerned, the largest useful aperture (for v = 2' as in Tables I. and IL.) is a 1 N
N 2 (264-5) * ” = 529° plification of the Microscope will be given by the general formula
above, if d is taken = 2°5. We then obtain, from a = d a
the maaimum aperture for every am-
N N a= 29" 500 ~ 200) and conversely N = 200.a as the minimum power required to enable the eye to admit all rays which emerge from the ocular. An aperture of 0°5 (60°) will therefore be useless in every respect (in regard to light as well as delineating power) as long as it is applied with powers of less than 100 diameters, and the same will be the case with an aperture of 0°25 (29°) for all powers below 50 diameters. Moreover, proper utilization of the rays which are admitted through a given aperture, will require still further restriction. For if the diameter of the pencils at their emergence from the ocular should closely approach the pupils’ diameter the least motion of the eye will cause a stopping-off of this or that portion of the aper- ture. The observer will therefore seldom utilize the full pencil, and will have the awkward sensation of a continual change of the illumination of the image.
All this considered, it must be concluded that the wtmost amount of aperture which can be really useful under the general circumstances of microscopical work, will be, for every power, about twice the figures indicated by the second table. This corresponds to an increase of the emergent pencils to a diameter of nearly 2 mm. (1°9 mm). Every larger proportion between aper- ture and power must be considered as decidedly irrational, because it is not only waste of aperture in every respect, but at the same time a positive disadvantage for convenient and proper observation.
Up to the limit here assigned, I admit the benefit of increased aperture, so far as the ower and lowest powers are in question, for which the other requirements—as has been shown—do not impose greater restrictions. In my opinion, the benefit of the increase is, however, not so much the gain of light by itself, but rather the ad- vantage, that narrower illuminating pencils, which do not fill wp the whole aperture of the objective, may be applied without incon- venient reduction of light. The smaller apertures which are sutti- cient for properly utilizing the delineating power of the objectives would also be quite sufficient in regard to light, provided the inci-
472 Transactions of the Society.
dent beam always utilized the full area of the objective. In point of fact, a system of a = 0°2 (23°) applied with a power of 106 diameters will not show any want of light under that condition, even with dull daylight. The deficiency which, under all circumstances, is found in the use of high powers (notwithstanding correspondingly wider apertures) has no other cause but that we are not allowed to apply illuminating pencils as large as the full aperture of the Micro- scope. With the exception of some particular cases, the utilization of wide apertures in observing delicate objects will always require such narrower incident beams of light (generally of no greater angle than 30—40° in air) as utilize directly a small portion of the aperture- area only; the effect of the wider aperture being to collect those rays which are dissipated to large angles by the structural elements of the objects. The actual brightness of the image which is ob- tained under these circumstances is of course much less than it would be if an illuminating pencil equal to the full aperture could be employed. The proper effect of low apertures is, it is true, much less dependent upon the reduction of the illuminating beams. Nevertheless, such reduction—by means of diaphragms below the preparations—is an important benefit in many observations. or that purpose it is of practical importance that the aperture should be greater than would be required for the brightness of the image under full illumination. If twice the value of a assigned by Table II. is admitted for the several powers, these powers will still afford sufficient light, even if incident pencils of half the aperture only are used for illumination, and three-quarters of the clear area therefore is left for the utilization of dissipated rays.
4. We have now all necessary data for defining, at any rate in outline, a rational standard for the ratio between aperture and power in regard to the entire Microscope, i.e. the amplification of the ultimate image (without considering at present the participation of objective and ocular).
(1.) So far as those apertures are in question which cannot at the present time be overstepped, the aim must be to obtain the most perfect performance for those powers which are just sufficient for the full utilization of the delineating capacities of these apertures. The figures of N assigned by Table I. may thus indicate the par- ticular aims for the various kinds of lenses—dry, water-immersion, homogeneous-immersion—in regard to those values of a which must be considered as the practical limits for these various systems (i.e. about 0°95 for the dry, 1°25 for the water-immersion, and 1:45 for the homogeneous-immersion systems respectively). For the full development of every system a reasonable latitude for further increase of power, beyond the limits of strictly useful powers, must, however, be left.
The Relation of Aperture and Power. By Prof. Abbe. 473
(2.) So far as the medium powers are in question, which are below the limits of useful powers for the maximum apertures, but still above those amounts which could be obtained by very moderate apertures, a somewhat strict economy of aperture 1s indicated by important considerations in regard to the general demands of scientific work (penetration, working distance, &c.), because the disadvantage of superabundant aperture will be always greater than the possible benefit. For the medium powers in use, the figures of Table I. will therefore give the approximate limits of latitude which may be deemed reconcilable with a rational construction of the Microscope for scientific work.
(8.) Concerning the lower and lowest powers, a gradually in- creasing latitude is left for the application of wider apertures than would be theoretically necessary in regard to the delineating capacity required for these powers. A surplus of aperture in- creasing up to about 100 per cent. for the lowest amplifications, will be in favour of the dl/wminating power of the Microscope; a considerably greater excess will at all events be mere waste.*
* The concluding part of the paper—ii. Division of the Entire Power of the
Microscope between Objective and Ocular—-will be printed in the next number of the Journal,
474. Transactions of the Society.
XII.—Description of a Simple Plan of Imbedding Tissues, for Microtome Cutting, in Semi-pulped Unglazed Printwng Paper. By B. Wiis Ricnarpson, F.R.C.S.1., Vice- President University of Dublin Biological Association.
(Read 10th May, 1882.)
I am emboldened to publish the following description of a method for imbedding tissues of suitable consistence for microtome cutting, as it may have some claim to originality, imbeddmg in semi-pulped paper being unnoticed in any of the standard works on microscopic manipulation which I have had opportunities of searching. Be this as it may, very thin and perfect sections can be cut with rapidity in semi-pulped paper, from either animal or vegetable structures of sufficient firmness to remain uninjured while being sent home in the microtome well. I think, however, that im- bedding in semi-pulped paper will probably be found to have a more extended range of usefulness for vegetable section-cutting rather than for cutting animal structures.
Although tissues submitted to the process should have a certain amount of firmness, as I have just observed, they should not, on the other hand, be so dense as to offer much resistance to the knife, very unresisting structures being unsuitable for this mode of imbedding.
The diameter of the tissue to be cut should, when feasible, be one-quarter of an inch less than the diameter of the microtome well. Indeed, a microscopist’s laboratory ought to be provided ~ with microtomes haying wells of different diameters that both time and tissues may be economized.
Stems of plants previous to cutting may, with advantage, be stored in methylated spirit for a few weeks; and animal structures, in whatever fluid has been found most appropriate for their pre- servation and, if necessary, for their hardening.
I shall now give the steps of this easy method :—
Cut strips, eight to nine inches long, from white unglazed printing-paper, the width of each strip to be a little more than the length of the structure to be imbedded. ‘Transfer the latter from the preservative fluid to filtered water, in which leave it for about half an hour, then dip one of the strips of paper in the water for a few seconds, remove it and drain the water rapidly off its surfaces. Take the structure to be cut out of the water, apply one end of the wetted paper to a portion of its circumference, and roll the paper around the structure as closely as the paper will allow of without tearing. If necessary, apply more wetted paper until both the paper and inclosure form a plug that should require a little
Simple Plan of Imbedding Tissues. By Dr. Richardson. 475
pressure for sending it home in the microtome well. If too much paper has been applied, tear off the superfluous portion until the desired calibre is attained.
The paper when wetted will, of course, stretch, but a little practice soon teaches the operator to roll it with only the tightness necessary for allowing the imbedded tissue to be cut without break.
In careful hands dozens of perfect sections may be cut in half an hour from very delicate stems } of an inch in diameter, or from the delicate aereal-roots of certain orchids. But I should mention that a pine-apple stem of an inch in diameter has afforded me most perfect sections when imbedded in the semi-pulped paper.
Up to the present time (April 1882) the only animal structures I have had leisure to imbed and cut in semi-pulped paper were decalcified human teeth, and a diseased external iliac artery removed from the body of a child, one of whose lower extremities I removed by amputation at the hip in March 1879.
From the “dentinal cartilage” I obtained several thin and instructive specimens.
The artery did not bear the knife to my satisfaction, having partially “rotted” from a too prolonged immersion in Miller's fluid.
Further experience of pulped paper as an imbedding medium may lead to an extended use of the paper for animal-tissue section- cutting. But I prefer to conclude here, at all events, with a stronger recommendation in favour of pulped paper for supporting vegetable tissues in the well of the microtome under the restric- tions I have mentioned. It is almost superfluous to add that each section should be floated off the knife in water, and that a little of the latter should be carried by the blade to the semi-pulped paper in the well, to maintain it at the requisite degree of saturation for efficient cutting.
The advantages which I consider the method to possess are :— (1) Facility in application ; (2) almost unlimited application in vegetable section-cutting under the restrictions above mentioned ; (3) rapidity in cutting; (4) the tissues are equally supported ; (5) cleanliness; (6) heat not being used, the subsequent staining of sections is more equal.
476 Transactions of the Society.
XIII.— Note on the Rev. G. L. Mills’ Paper on Diatoms in Peruvian Guano. By F. Krrtoy, Hon. F.R.MS.
(Read 14th June, 1882.)
Tn the last volume of the Journal, p. 865, Mr. Mills has figured and described a new species of Auliscus, A. constellatus. After reading his description and carefully examining his excellent figures, I was satisfied that his species was identical with that described by Herr Janisch in his ‘ Zur Charakteristik des Guanos,’ Breslau, 1861-62, as A. Stockhardtiz; it is also figured in Schmidt’s ‘ Atlas der Diatomaceen-Kunde,’ Tafel xii. figs. 11-13. Schmidt remarks that fig 13 = “A. racemosus Ralfs (Gre- ville Monograph of the Genus Auliscus, T.M.S. vol. xi. 1863, p. 46, pl. iii. fig. 18) doch Janisch’s Benennung ist alter.” This is undoubtedly correct, and Ralfs’ specific name must be deleted.
I communicated the result of my examination to Mr. Mills, who at once admitted the correctness of my views, and, moreover, had the kindness not only to send me the specimens of his sup- posed new species, but also most generously gave me his specimen of Aulacodiscus Kittont with fourteen processes. On examining this I congratulated myself on possessing a probably unique but certainly a very beautiful state of this species. Zxamining it again a few days afterwards, I found, in consequence of the balsam being still soft, that a valve of Aulacodiscus Comber had partially shipped over it. I resolved upon remounting it, and succeeded in placing it on another slide; during the process I caught a glimpse of the f.v., which induced me to examine it again very carefully with a binocular and + objective, when to my disappointment I found that our supposed fourteen processed A. Kzttone was composed of the two inner valves (each with seven processes) of a double frustule ; these were in close proximity—in fact, the two convex surfaces touched each other, the elevations on one surface fitting into the concayities of the other, thus accounting for the fact, noticed by Mr. Lewis, that the processes appeared “all in the same plane, and all equally and distinctly defined.” The number of processes in Aulacodiscus and Ewpodiscus are now generally admitted to be of no specific value, but it is more constant in some species than in others, e.g. A. formosus. I have never seen more than four processes, and on some valves I have observed as few as three, but in every case they were abnormal forms. In all other species the number is more or less variable. In a pure and recent gathering of A. Kittons I have seen no valve with more than six processes, four being the usual number, but abnormal forms are by no means rare. I have seen a six-rayed valve with four of the rays at right angles to each other,
Diatoms in Peruvian Guano. By F. Kitton. 477
the remaining two being close to the opposite rays (processes). The most remarkable abnormally is a valve without process or avra€, but with the former faintly indicated near the margin.
It is only right to add that these remarks on Mr. Mills’ paper have been written at his request, as he does not wish an error to remain uncorrected.
478 SUMMARY OF CURRENT RESEARCHES RELATING TO
SUMMARY
OF CURRENT RESEARCHES RELATING TO
ZOOLOGY AND: BO] snes
(principally Invertebrata and Cryptogamia),
MICROSCOPY, &c.,
INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.*
ZOOLOGY.
A. GENERAL, including Embryology and Histology of the Vertebrata.
Division of Embryonic Cells in the Vertebrata.t—L. F. Henné- guy, in studying cell-division as exhibited in the ovum of osseous fishes, finds that that of the trout, on the third or fourth day after fecundation, if treated with a mixture of acetic and picric acids, is the best adapted for this investigation; the cells are then seen to be formed of a finely granular protoplasm, and contain a nucleus of some size.
The nucleus of acell in a state of repose contains a plexus, formed of small irregular granulations, which are especially well stained by carmine. The nucleolus is only a little larger than the other granu- lations. Soon there appears around a clear space, of which the centre is occupied by the nucleus, very fine clear lines, which are set along the rays of the cell, and which together form an aster; this aster elongates and becomes elliptical, as does also the nucleus; the aster then divides, and the two halves each form a fresh aster; at this moment the membrane of the nucleus disappears, and the rays of the aster penetrate into the interior. The plexus now breaks up into a number of small rod-shaped bodies ; these become set at the extremities of the rays, and form the so-called equatorial plate. Gradually the rods diminish in size but increase in number, and fuse to form a pectinate figure. The body of the cell then begins to be constricted in its middle, the rays of the aster disappear, and the connective filaments alone remain to unite the two nuclei, until at last the cells become completely separate. The new nucleus, due to the fusion of the rods, is highly refractive, and is intensely coloured by reagents ;
* The Society are not to be considered responsible for the views of the authors of the papers referred to, nor for the manner in which those views may be expressed, the main object of this part of the Journal being to present a summary of the papers as actually published, so as to provide the Fellows with a guide to the additions made from time to time to the Library. Objections and corrections should therefore, for the most part, be addressed to the authors. (The Society are not intended to be denoted by the editorial ‘‘ we.”)
+ Rey. Internat. Sci. Biol., ix. (1882) pp. 363-5,
ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 479
as it increases in size, there appear the limiting membrane and the internal plexus.
At a later stage of development, when there has been multiplica- tion of the cells, these become smaller and smaller, and the asters gradually become quite indistinct. In the earliest stages of segmen- tation the process of division is more difficult to follow, owing to the large size and very granular contents of the cells; on the first and second day the cells become so uniformly tinted that the nuclei are with difficulty made out. As the cells diminish in size the action of the colouring matter becomes more and more confined to the nucleus, and the author is of opinion that the chromatin of Flemming is at first uniformly distributed through the cell, and that it gradually separates to form a constituent of the nucleus.
Genesis of the Egg in Triton.*—Mr. T. Iwakawa records the result of observations on the genesis of the egg of the common Triton (T. pyrrhogaster Boje), in which he describes the manner of depositing the egg (the female turning upside down so as to place it under the leaf or stem), the structure of the ovary, origin of the ovum and Waldeyer’s “epithelial islands” (the author’s view being that the ovum does have an epithelial origin), the formation of yolk- spherules, the vitelline membrane, the germinal vesicle, and the “ yolk- nucleus.”
Formation of Fibrine.t|—In 1879 Dr. Norris described the alleged discovery of a third corpuscular element in blood in the form of colourless disks, which he considered to be an earlier stage of the red corpuscles. { This was criticised by Mrs. Ernest Hart in the fol- lowing year, § her view being that they were red corpuscles that had undergone post-mortem changes prior to taking part in the formation of fibrine.
Continuing her investigations and repeating the experiment of “isolation ” || a great number of times, she began to observe that the appearances changed according to the length of time which elapsed between the spreading of the layer of blood between the two glass surfaces and the moment when the cover-glass was raised, and thus discovered that a whole series of phenomena could be traced, leading from the pale or colourless corpuscle up to the complete formation of networks or bands of fibrine. In developing this method of working it was found that the staining reagents recommended by Dr. Norris were not sufiiciently powerful to bring out all the details that could be observed on the glass surfaces, and after many trials a highly con- centrated solution of nitrate of rosanilin in absolute alcohol was found to be the best staining reagent. The method adopted was to detach the cover-glass from the slide after the corpuscles had been fixed by osmic acid vapour, and to examine both the surfaces of the cover-glass and the slide, to see which presented the most perfect preparations.
* Quart. Journ. Micr. Sci., xxii. (1882) pp. 260-77.
+ Ibid., pp. 255-9 (1 pl.).
t See this Journal, iii. (1881) pp. 229-32. § Loc. cit. || See description, loc. cit.
480 SUMMARY OF CURRENT RESEARCHES RELATING TO
Having made a selection, a drop of the concentrated solution of nitrate of rosanilin was deposited on the glass and allowed to remain for a few moments, and then washed off with a fine jet of distilled water. The red, pale and colourless corpuscles, with their ramifications and the most delicate fibrils of fibrine, then become visible under a high power. The preparations may be mounted dry, and will keep for a great length of time. If the process be performed as rapidly as the dexterity gained by an oft-repeated experiment will allow, it will be observed that the circular appearance of the corpuscles is perfectly preserved, and that every shade of colour may be found, from the normal red corpuscles down to the colourless Norris corpuscle, which only takes the faintest tint of pink. If, however, the glass surfaces be allowed to remain in contact for a moment, the colourless cor- puscles are found to have lost their globular form, and to have become pyriform or elongated. On leaving the glass surfaces still longer in contact, these pale corpuscles are observed to undergo a remarkable change. They send out long processes or tails, which bifurcate and divaricate in every direction. On allowing a still longer interval to elapse, so that itis more than probable that coagulation would occur in a film of blood lying between two glass surfaces, and on separating these surfaces, perfect specimens of fibrine may be obtained after staining. On now searching the field, the pale corpuscles, which could formerly almost always be discovered, are nowhere to be found, and the conclusion is forced upon one that the branching corpuscles have developed or broken down in fibrinous threads. Small granules are, however, found from which threads of fibrine appear to spring. These granules are described in Ranvier’s ‘Traité Technique d’Histologie’ as the centres of fibrine formation. They appear to the author to be all that is left of the pale corpuscles, whose intermediate transformations have not before been recognized, but may perhaps be identified with the appearances and changes described. Amongst other figures, one is given showing the departure of the fibrils of fibrine from the pale corpuscles.
New Blood-corpuscle.*— According to G. Bizzozero, if the circu- lating blood in the small vessels of the mesentery of chloralized rabbits or guinea-pigs is observed under a high power, there will be seen, besides the ordinary red and white cells, a third form of cor- puscle which is colourless, round or oval, and from one-half to one- third the size of the red corpuscle. He considers that they have hitherto escaped the notice of observers (1) owing to their translucency and want of colour; (2) because they are less numerous than the red, and less visible than the white corpuscles ; (3) owing to the great difficulty of observing the circulating blood in the small vessels of the warm-blooded animals. They can be seen also in freshly drawn blood, for the most part aggregated around the white corpuscles, or immediately under the cover-glass, to which they adhere. They soon become granular, and give rise to what is called the granule- masses. ‘Through appropriate reagents their form can be preserved.
* Arch, Ital.de Biol., i,(1882) pp. 1-4; cf.‘ The Microscope,’ ii. (1882) pp. 59-60.
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 481
A solution of salt coloured with methyl-violet has this property. The best method of examining them in the human subject is to place a drop of the above coloured solution over the puncture and mix the drop of blood thoroughly with it.
Owing to their typical forms, it is very unlikely that they are derived from the red corpuscles. The colourless corpuscles contain no ingredients from which they could be derived. After bleeding, and in many diseased conditions, they are increased in numbers. They play an important part in the formation of thrombi and the coagula- tion of the blood, which has been attributed by Mantegazza and Schmidt to the white corpuscles, because the latter are few in number in the circulating blood, and their destruction was never observed by Bizzozero, provided the blood was mixed with a saline solution, Again, the time at which coagulation sets in corresponds very closely to the time that these new corpuscles undergo degeneration. The fluids which retard or prevent coagulation—as solutions of carbonate of soda and sulphate of magnesia—have the same action in pre- venting the granular degeneration of these corpuscles. An indif- ferent solution of salt does not preserve them, but one to which the methyl-violet has been added does.
From this evidence it appears (to the editor of the ‘ Cincinnati Medical News’) highly probable that the formation of fibrine takes place under the direct influence of these corpuscles. To them Bizzo- zero gives the name of “ Blutplattchen.”
Life and Death in the Animal Organism.*—After completing an important investigation on the “ Earliest developmental operations in the ovum, on cell-division, and on conjugation in the Infusoria,” O. Biitschli, early in 1876, wrote an essay headed “ Thoughts on Life and Death,” but he left it unpublished, considering, on the one hand, that his ideas on the differences between Protozoa and Metazoa in respect of the phenomena of death were too recently acquired to be made known, especially in print, and that, on the other hand, the speculations which he had associated with these ideas were too immature to be made permanent. His fundamental views, however, namely those relating to the non-existence of individual death in the Protozoa, have now been published.
“Tf we glance over the phenomena of the origin and destruction of beings in the great series of animal organisms, we are astonished by a significant contrast in the importance of individuality in the higher, i.e. the many-celled, as compared with the lower, i.e. the uni- cellular, forms, the Infusoria or Rhizopoda. Whilst in the first the individual, in almost all cases, asserts an existence definite and distinct even from its progeny, in the unicellular forms, on the contrary, which reproduce by fission, we are met with the fact (which does not usually receive much attention) that at the time of reproduction the individual, as such, ceases to exist, and divides its individuality equally between the individualities of its two offspring, which now come into existence. This remarkable phenomenon
* Zool. Anzeig., v. (1882) pp. 64-7. Cf. Naturforscher, xv. (1882) pp. 125-6, Ser, 2.—Vor. II. 2K
482 SUMMARY OF CURRENT RESEARCHES RELATING TO
appears in the most striking light when we endeavour to realize in these lower forms the idea of death, such as we have been led to consider it from observations of the higher animals. Death in the higher organisms is not the total extinction of life, but only of the individual existence; bat the reproduction of a unicellular organism constitutes at the same time its death. On the other hand, however, by the idea of death in the higher organisms is implied an actual separa- tion of organized substance from the activity of life, in other words, an annihilation of previous life. This element is entirely wanting in the individual death of the Protozoa, that is, in its reproduction ; it goes on living all the same, though in the persons of its progeny.
If we study the development of certain Protozoa,—the Infusoria,- — we come upon the highly remarkable fact that death does not occur in them, in the sense of annihilation of organic material and from causes inherent in the organism itself. Although these organisms, in the course of their life, are threatened by death under a thousand forms, yet this takes place by “accidents,” and thus the few individuals which reproduce the species are to be considered of equal importance with the multitude which perish, for the few reproduce by fission only, and are thus immortal; while the many which die could have repro- duced their species just as well as the others, if they had had the same favourable opportunity; not one of them necessarily carries in it the seeds of death.
Whoever wishes to construct a hypothetical representation of the fact that in the higher animals the individual is limited in its dura- tion to a certain time, will find a tolerably simple plan open to him. If we hold it to be allowable to consider the peculiar vital manifesta- tions of the cell, the fundamental element of every form of organiza- tion, as caused by the presence of a substance which acts in a certain sense like a ferment,—necessary to the production of those chemical changes in the cell which result in vital manifestations, but gradually, though perhaps slowly, used up,—then the limited duration of the life of one of the higher animals may be intelligibly represented by assuming that the ovum out of which this organism once originated acquired a certain amount of this ferment-like substance, which is gradually exhausted during life, and with the final exhaustion of which the end of the individual existence coincides.
It is otherwise with the Protozoa, which reproduce by simple division. These organisms have also this characteristic vital ferment, but they also enjoy the peculiarity of being able to renew it ; hence it is not exhausted in them, and they are not overcome by death in con- sequence of its being used up.
But the power of forming this vital ferment is shared by the higher organisms as well, but here it is localized, being confined to the generative organs. In the other cells composing the body the material we have been speaking of is gradually and increasingly used up in the course of their active existence; but in the generative regions, whose cells maintain their primitive character longest, fresh vital ferment is accumulated for their posterity. Certain appearances occur which, perhaps, justify us in forming an approximate idea as
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 483
' to the place in the cell which this material with its property of evoking life occupies. Among these the chief are the phenomena of conjugation of Infusoria, taken in connection with facts recently acquired in the study of the process of fertilization in the Metazoa. The gradually diminishing vital energies of the Infusoria are strengthened afresh by conjugation, and this comes about by a partial or total renewal of the nucleus from the so-called nucleoli or primary nuclei. A total or partial renewal of the nucleus of the ovum is also seen in fertilization, and it is most probably effected by the spermatic nucleus.
(This passage was written in 1876, when the first and imperfect account of the process of fertilization had just been put forth; but it would be easy to alter it so as to bring it into accordance with our present knowledge, without interfering with the part played by the nucleus.)
Thus the failing vital powers of the Infusoria are raised up again by the renewal of the nucleus, and a similar result occurs in the process of fertilization; is it not, therefore, a justifiable conclusion that the vital ferment which has been spoken of, actually resides in the nucleus of the cell, whenever this is present. It is not the whole nucleus which is to be interpreted in this way, but only a small part of its bulk. Thus in the case of the Infusoria, it must be assumed that the freshly produced life-ferment is collected more especially in the so-called nucleoli, but in higher organisms in the reproductive cells, chiefly in the nucleus of the male reproductive elements.”
N. Cholodkowsky, in discussing * the doctrine of Biitschli, points out certain difficulties in the way of our accepting this view. Some forms, e.g. Hydra, have an asexual as well as a sexual method of reproduction ; now, if all the cells of such an animal have the power of producing new individuals they must all be immortal; yet, as a matter of fact, we know that many die down. It seems to Cholod- kowsky that the cause of the death of the Metazoa is to be sought for in the multicellularity of their organism. A cell has in itself and for itself a potential immortality; but as soon as differentiated cells are united into an individual there commences amongst them a struggle for existence, which, eo ipso, leads to destruction. The hypothesis of Butschli recalls the Darwinian doctrine of Pangenesis ; just as Darwin supposed a general distribution of reproductive cells throughout the organism, which only later became concentrated in the generative cells, so does Butschli deal with his vital ferment, and the doctrine of the latter is therefore only a more physiological way of expressing that of Pangenesis.
Pelagic and Deep-Sea Fauna.jf—T. Fuchs enumerates the distinguishing characteristics of the pelagic and the deep faunas respectively, and makes some inductions as to the reasons for these peculiarities. Pelagic animals are those which are wholly indepen- dent of the shore and the sea-bottom at all stages of their existence.
* Zool. Anzeig., v. (1882) pp. 264-5. ‘
+ Verh. k. k. Geol. Reichsanstalt, 1882, pp.49 and 55. Cf. Naturforscher, xv, (1882) pp. 199-202.
ae 2
484 SUMMARY OF CURRENT RESEARCHES RELATING TO
Most of them are transparent and colourless, and thus invisible in water; where colour occurs, it is usually violet or blue, resembling that of the water; the fishes are chiefly stcel-blue above, silvery-white below. Most forms are naked; the shell, if present, is comparatively delicate. A large number are viviparous, even when their nearest allies are oviparous.
A great number of pelagic animals are phosphorescent. Nearly all are admirable swimmers. Some have their surface-area largely developed, e. g. the tests of Radiolaria, of Globigerina, Hastigerina, &c., probably in order to hinder sinking. As to the manner of life, they are almost without exception social, they mostly have a very wide distribution, and are found alike in the Atlantic, Indian, and Pacific Oceans; the genera are almost all identical in these seas, although polar seas are distinguished from warmer waters by possessing few forms besides Crustacea, Pteropoda, Cephalopoda, and Cetacea. In connection with their usually delicate structure stands the fact that it is only in the calmest weather that they live on the surface; storms may drive them to a depth of more than 50 fathoms. Further, far the majority only come to the surface in the night, a point to be con- sidered in connection with the prevalence among them of phosphor- escence; the time of appearance of the phosphorescent fish is more often connected with the night than with any other time. Pelagic animals seldom occur except over deep water, and at great distances from coasts, hence their scarcity in the German Ocean, their poverty in littoral and their abundance in deep-sea deposits.
The deep-sea fauna is distinguished by the appearance or pre- dominance of certain individual species, genera, and families, and exhibits little variation in the different parts of the world. It com- mences at a depth of about 50 fathoms in all seas, but it is only in the tropics that anything like a sharp line of demarcation is found between it and the littoralfauna. Examining these points to ascertain the reason for a bathymetric limit of this particular nature, Fuchs finds that it cannot be due to temperature, although this diminishes as the depth increases, for in the Red Sea the warm zone extends much below 50 fathoms, while in polar waters even the surface has a low temperature, and currents operate besides so as to introduce great irregularity into the bathymetric relations of temperature ; however, the fact that 48 to 50 fathoms has been ascertained to be the limit to the penetration of light into the sea appears to him good evidence that the presence or absence of light is the determining agency sought for, and that the littoral fauna is simply the fauna of the light, the deep-sea fauna that of darkness. ‘This view is supported by the more superficial distribution of deep-sea forms in some places in which the limit of light lies at an inferior depth, and the deeper range of littoral forms in fresh waters, where the light has greater penetration. The large eyes or blindness of so many, the pale or monochromatic colour of most, and the phosphorescence of a large number of the animals which compose this fauna is evidently connected with the absence of light. The resemblance of the pelagic to this fauna is intelligible if it is remembered that it too is most in its element in
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 485
the darkness. Resemblances between cave faunas and that of the deep-sea point also to a common cause in the absence of light. The range of some littoral forms into great depths may perhaps be found to be due to their being nocturnal in habits.
The cavities which occur under coral reefs off Brazil may perhaps shelter a fauna of deep-sea character, owing to the absence of light there; hence it would be not unlikely that geologists might find similar aggregations of deep-sea animals in formations otherwise composed of littoral reefs. Otherwise the relations of deep and littoral faunas were probably much the same in geological times as now, owing to the similarity of their relations to the light, and the differences here indicated can, in point of fact, be traced throughout all formations.
B. INVERTEBRATA. Mollusca.
Anatomy and Classification of the Cephalopoda.* — Dr. J. Brock commences with a study of Rossia, the knowledge of the anatomy of which is confined to the short description given by Prof. Owen. Asa result of the new investigations we find that Rossia is, as has been supposed, most closely allied to Sepiola ; the relations of these two forms to the Myopsida, and especially Sepia and Loligo, are by no means so clear. The author’s earlier investigations led him to the belief that the affinities of the different forms might be well shown by this diagram :—
Sepia.
—Rossia——_——Sepiola. —Loligo. —Ommastrephes,
The presence, however, in Rossia, of fused lower salivary glands points to its affinities with the Cigopsida, and this would lead us to form a table in which Loligo should stand above Rossia, or nearer Sepia. As to the relations of Sepiola to the form last named, it might be supposed that Sepiola had branched off from the Decapod stem independently, but the Octopod characteristics of Sepiola, as seen in its musculature, are to be found also in Rossia, and it requires evidence of a kind very different from that which we have at present to lead us to believe that these very similar arrangements could have been independently developed by the two forms. The Octopod type of the musculature of Rossia is still further developed in Sepiola, and that in a way which justifies us in regarding the latter as a direct descendant of the former. A useful table is given in which are enumerated twelve characters and the respective resemblances and differences of Ommastrephes, Rossia, and Sepiola.
If the view that Rossia and Sepiola form a line of development which branched off from the Decapod stem shortly before Loligo be
* Zeitschy. f. wiss. Zool., xxxvi. (1882) pp. 543-640 (4 pls.).
486 SUMMARY OF CURRENT RESEARCHES RELATING TO
correct, we find in it what may be spoken of as parallel-developments ~ with the Myopsida and Octopoda; we find, that is, in this side
branch a series of differentiations which have, for the different organs, _ a most remarkable resemblance in those two series. Just as from Loligo to Sepia, so from Rossia to Sepiola we find the upper salivary glands lost, the accessory nidamental glands fused, the efferent duct of the ink-bag sharply marked off, and the lateral teeth disappearing from the middle plate of the radula. From Ommastrephes to Sepia, just as from Rossia to Sepiola, the fused lower salivary glands are separated, and there appears a characteristic arrangement. of the ova in the duct. Likewise, there is in Sepia and Rossia a shortening of the inner pallial nerves, which finds its termination in the absence of these in Sepiola on the one hand, and the Octopoda on the other. A very instructive diagrammatic table is given by the author to demonstrate the points on which he insists.
If we enter into still wider generalizations, the facts observed by the author lead us to see that in the Dibranchiate Cephalopoda, long before the separation of the phylum into the Octopoda and Decapoda, there must have been a tendency, under suitable, though still un- known, conditions, for the cartilaginous articulations with the mantle and funnel to yield to firmer membranous or muscular cephalic joints ; thrice, or twice at least, did this tendency exert its influence. In connection with this there must also have been a tendency to the reduction and final loss of the upper salivary glands, the separation of the lower ones, and the fusion of the accessory nidamental glands.
Dr. Brock then passes to a second study of the generative organs of the Cephalopoda; in dealing with the female organs of the Cigopsida it is pointed out that the nidamental glands may be absent, as in Enoploteuthis, or that they may be present, with (a) the oviduct lying ventrally to the gills, as in Ommastrephes sagittatus, or (6) the oviduct may open with a buccal invagination of the integument, lying dorsally to the gills, as in Om. todarus, Onychoteuthis, or Thysano- teuthis.
A study of the generative organs of the Philonexide shows, us that they may be thus arranged :—
1. Subfam. Hectocotylifera. ¢ with a free Hectocotylus.
a. Philonexide S. Str. Hectocotylus without dermal frills. No water-vascular system—Argonauta, Philonexis.
b. Tremoctopodide. Hectocotylus with dermal frills. A water-vascular system—Tremoctopus.
2. Subfam. Parasiride. Free hectocotylus not known, but pro- bably present. @ with very long oviducts, viviparous. Parasira. -
In dealing with the gland of the oviduct, it is pointed out that —
the following series may be detected in the Octopoda :—
1. Gland consisting of a series of ceca arranged radially around the oviduct; no increase in the extent of the secreting surfaces —Argonauta.
2. The secreting surfaces of the gland well developed, and a
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 487
circlet of strongly developed receptacula seminis interpolated between the gland and the oviduct—Tremoctopus violaceus.
3. The receptacula seminis not so well developed; a fresh gland developed between them and the primitive gland—Parasira catenu- lata.
4, No receptacula seminis; the walls of the primitive and of the secondary gland highly developed, and in the latter so far advanced as to lead to a fusion of the glandular sacs—Octopus, Eledone.
Various as are the forms of the oviducal gland in the Octopoda it is important to notice how uniform they are in the Decapoda.
The author then enters upon a consideration of the so-called water-canals and the viscero-pericardiac cavity; he finds that the genital capsule of the Octopoda is the (reduced) direct homologue of the viscero-pericardiac cavity of the Decapoda; and that the water- _ canals of the Octopoda correspond to the anterior, while the genital capsule corresponds to the hinder portion of the viscero-pericardiac cavity of the Decapoda. And he concludes with accounts of Tremoctopus ocellatus n. sp., Octopus pictus n. sp., Loligo bleekeri, and Cranchia reinhardti.
Ink-Sac of Cephalopoda.*—P. Girod publishes a full and detailed account of his study of this organ.f By a careful dissection, first of the peripheral trabeculze, and then of the apex of the pyramid formed by the formative zone, we come upon the cellular mass which forms the central portion of the trabecule. When a portion of the tissue of this part is teased out, elongated cylindrical cells may be detected which, in their general character, are not unlike the cylindrical cells of many mucous membranes; the large nucleus which occupies the narrower end of the cell becomes very apparent on the addition of colouring reagents. The cell itself, on high mag- nification, is found to be divisible into two portions: the larger of these is coloured yellow by picrocarmine, and seems to be formed of a hyaline liquid, which is limited on the nuclear side by a faint, slightly concave, and granular line ; the second and narrower portion contains a granular protoplasm. The constitution of the cell sug- gested to the author that it belonged to the calyciform series, but the absence of any orifice did not seem to him to justify that view. Near these cells others may be seen which contain black granula- tions in their upper portion; these are not cylindrical, but are divided by constrictions into three portions ; the uppermost colour- ing matter is bounded externally by the cell-membrane, and is also distinctly separated from the nucleus. On the whole, there is a very close connection between these and the cells of the first set, the hyaline mass in the latter being now filled with pigmented granula- tions, and the part which contains the nucleus having been elongated. Other cells present other characters ; in some there is a much larger aggregation of pigment, whence two lateral prolongations descend, one on either side of the nucleus: here, too, slight pigmented granu-
* Arch. Zool. Expér. et Gén., x. (1882) pp. 1-100 (5 pls.). t See this Journal, i. (1881) pp. 227, 586, and 876.
488 SUMMARY OF CURRENT RESEARCHES RELATING TO
lations are to be seen within the substance of the nucleus. In others the black granulations are so richly developed as to completely obscure the nuclear mass, although that body is still present. Finally the cells commence to undergo degeneration, their membrane breaks, and the pigment escapes ; the nucleus, however, still persists, and it is in consequence of this that we find free nucleated masses in the midst of the pigmented granulations. The author discusses in order the histological characters of the meshwork, the wall of the pouch, its internal, median, and external tunics.
Turning to the development of the ink-sac, we find that on the fourth day of the second period (that of the development of the organs) the anal depression comes in contact with a process of the mesoderm, and then divides into two portions, the superior of which is the ink-sac, and the inferior the rectum. The former rudiment has at first a transverse direction, and extends from the anal orifice to the internal yolk-sac, and is clothed by a single layer of epithelial (ecto- dermic) cells. This is what will form the vesicle. The cells at the cecal extremity soon begin to multiply and form a thickening which is the rudiment of the gland. The glandular mass developes rapidly by making its way into the midst of the mesoderm; the cells of that layer now begin to form peripheral layers around the gland, till they nearly completely surround it, and the mass becomes divided into two lobes, between which there is an extension of the mesoderm. Changes in the cells themselves now appear, and give rise to the formation of a thick granular liquid. As soon as the glandular cavities are developed the investing cells take on the characters which belong to the formative zone of the adult, and a peripheral and a formative zone are thus developed. Further changes bring about a connection between the gland and the reservoir; the latter then begins to increase rapidly in length, and at the same time to dilate. Still further changes, in the mesoderm, give rise to the different investing layers, and there is some alteration in position. Looking more generally at the matter, we find that the ink-sac is formed by an epidermal invagination, which, during development, is differentiated into two parts, the gland and the vesicle (reservoir) ; this invagination is contained in a kind of mesodermic sac, which forms the tunics that envelope the epithelium ; the innermost of these consists of an epithelial and of a connective layer, the median of the silvery and of a muscular layer, and the outer of connective tissue. When we compare this with the integument, we cannot but be struck with the remarkable similarity between them ; there, too, we find an epithelium, the cells of which are arranged in a single row, and limited externally by a thick cuticle; the connective layer contains the chromatophores, and beneath this there are a silvery layer, muscular fibres, and a layer of connective tissue. The absence of chromatophores in the region of the sac may be explained by a study of the intermediate stages presented by different parts of the body.
The researches of Lacaze-Duthiers on the purple-glands of certain Gastropoda have led the author to make a study of these structures, from which it results that their anal gland is homologous with the
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 489
ink-sac of the Cephalopoda, and this view is strengthened by a consideration of the nervous supply. In the Gastropoda the glands in question receive filaments from the “‘ asymmetrical centre,” in the Cephalopoda the nerves come from the visceral or inferior ganglion which corresponds exactly with that centre.
If we compare the ink-sac of the Octopoda with that of the Deca- poda we find that there is in the former an arrest of development, the reservoir not being elongated or widened out; in consequence of this close relations still obtain between it and the anal orifice, and the gland and reservoir are closely applied to one another. It is to be borne in mind that the tetrabranchiate Cephalopoda are without the organ, and that it is only some of the Gastropoda which possess one, and that that one is always much simpler in character.
The physiology of the question is also dealt with, and it is pointed out that three stages may be distinguished in the excretion of the ink: (1) there is a continuous passage of ink from the gland into the vesicle—due to a vis a tergo, and to the compression exercised by the limiting membrane of the gland and the nodosity of the vesicle; (2) an intermittent passage of the ink from the vesicle into the sac, due to the contraction of the vesicle; (3) spasmodic expul- sion of the ink by the funnel, due to the spasm of expiration. The nerve-branches from the visceral nerves were found to be motor filaments, presiding over the contraction of the wall of the vesicle.
Sense of Colour in Cephalopoda.t*—How highly developed the sense of colour is in insects has been shown by Sir John Lubbock in his interesting observations on bees, wasps, and ants. For the development of the same sense in animals of a different type C. Keller brings forward evidence taken from the cuttle-fishes, which manifest in a high degree the power of adapting the colour of their skin to that of the environment. Keller was able to observe this adaptation of colour in Eledone. In the Naples Aquarium a specimen of this Octopod was under the necessity of flying from a powerful lobster; during its flight it appeared pale red ; but subsequently, resting on a tuft of yellow rock covered with brown spots, it imitated the yellow ground- colour with its brown spots so closely that it became almost invisible to the observer. In this case the conditions were decidedly very favourable for the occurrence, for yellow and dark-brown colour-cells occur in Eledone in large numbers. It should be added that the eye of the cuttle-fish shows an unusually high development.
‘Foot’ of certain Terrestrial Gastropoda.t—Mr. J. Wood- Mason describes the structure of the part of the foot called by German writers on malacology the Fuss-sawm which, as no technical name for it appears to exist in the English language, he proposes to call the peripodiwm, in allusion to its relation of position to the locomotor ventral surface or foot of the molluscs possessing it, but which he thinks may be homologous with the lateral folds (epipodia)
* Vierteljahresschr. Naturf. Gesell. Zurich, xxvi. (1881) p. 100. Cf. Natur-
forscher, xv. (1882) p..40. + Proc. Asiatic Soc. Bengal, 1882, pp. 60-2.
490 SUMMARY OF CURRENT RESEARCHES RELATING TO
of many marine molluscs (Haliotis, e. g.). Very frequently the peri- podium is provided at its posterior extremity with a capacious pit, the capacity of which may be increased by the prolongation upwards of its anterior margin in the form of a horn, which not being specially sensitive is not a tentacle, often it is without this terminal pit; it is invariably richly ciliated throughout from the mouth on one side round to the mouth again on the other side dorsally; equally in- variably is it limited off from the side of the body (and frequently also from the muscular foot) by a peripheral groove, which deepens anteriorly. Its office is to assist in lubricating the foot, the pit when present receiving the effete lubricating fluid and throwing it off in gelatinous lumps.
The foot-gland, as is well known, pours out its abundantly ae constantly flowing secretion through an aperture which is situated below and a little behind the mouth into a hollow whence it naturally falls into the deep anterior end of the dorsal peripheral groove, whence again it is carried by the cilia with which the surface of the peri- podium is beset (being distributed to the foot as it goes) to the terminal pit. In those forms in which this pit does not exist, the secretion that has served for lubrication is merely left behind by the crawling mollusc.
As Pulmonata possessing a ciliated peripodium with and with- out a terminal pit are to be found in every quarter of the globe, and as it is in the highest degree improbable that so highly specialized a structure, subserving such an important purpose in the animal economy as this evidently does, has arisen independently many times in many different forms in many widely separated areas of the earth’s surface, the author considers that it has a higher taxonomic value than has hitherto been assigned to it, and he feels strongly inclined to distinguish those forms that possess it and those that do not (or have lost it) from one another by calling them Craspedophora and Lipocraspeda respectively.
Mucin of Helix pomatia.*—According to H. A. Landwehr, when the mucin of Helix pomatia is treated with 1 per cent. sulphuric acid, it yields grape-sugar, whereas mucin from other sources yields only a reducing substance. The grape-sugar cannot be derived from glycogen, since the iodine reaction fails entirely in the freshly expressed secretion, and in the mucin prepared from it. The author however, succeeded in obtaining a carbohydrate, for which he propeses the name “achrooglycogen.” In order to prepare it, he directs that the mucin obtained from the snails shall be treated with 5 to 10 per cent. caustic potash, and the proteids separated by Briicke’s solution (potassiomercuric iodide), the solution filtered, and the filtrate pre- cipitated by alcohol. The material thus obtained, after being washed with absolute alcohol and dried, is an amorphous, white, “tasteless powder, readily soluble in water. The solution is strongly opalescent, gives no iodine reaction, and does not reduce an alkaline copper
* Zeitschr. f. Physiol. Chem., vi. (1882) pp. 74-8. Cf. Journ. Chem. Soc. Abstr., xlii. (1882) p. 708.
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 491
solution. By boiling with acids, or by digestion with saliva or diastase, the substance is converted into dextrin and grape-sugar.
Rhodope veranii.*—Professor L. Graff gives an account of this form, which was regarded by Schultze as a Turbellarian, and named Sidonia elegans; he has been able to demonstrate that it is not a worm, but the Nudibranch long ago described by Kélliker under the name of Rhodope veranii. The largest examples are about 4 mm. long, with a breadth of } mm.
The integument consists of a single stratum of cylindrical epithe- lial cells, and is pretty closely invested by long cilia; this integument is pigmented, and a figure of the curious arrangement of the colour, under what the author regards as its typical form, is given. Cal- careous spicules, of some size, are to be found under two different forms, embedded in the parenchyma of the body. The mouth lies at the anterior end, but is sometimes held dorsally ; the cavity into which it leads is provided with closely appressed small papille, but there is no indication of anything like a radula. After some account of the other parts of the digestive system, of the nervous system, and of the generative apparatus, Dr. Graff states that, like Kélliker, he searched in vain for any indication of a heart or blood-vessels. The numerous small oval corpuscles which fill the ccelom were suspended in a colourless fluid, which appears to be set in motion by the move- ments of the body, or the contractions of the enteron. The author was, however, enabled to discover a water-vascular system similar to that of the Platyhelminthes. Strong magnification revealed actively moving flagella, scattered through the body, and similar to those which are found in the excretory system of various Vermes. Each flagellum is continued in a vesicular enlargement, and by its widened base completely closes the ciliated funnel, the free end of the flagellum being directed towards the efferent canal. No exact information can be given as to the branchings of the excretory system, or as to the character of its orifices.
The absence of gills, buccal mass, and radula, as well as of a vascular system, proclaims Rhodope to be the very lowest of all known Nudibranchs; at the same time it is distinguished from the allied Turbellaria by its anus, by the structure of its generative organs, its central ganglia, and its sensory apparatus. Rhodope must not, however, be supposed to have been derived from the present specialized Dendreceela, but from a group of Rhabdoccelida, to which, in his forthcoming Monograph of the Turbellaria, the author intends to apply the term Alloioccla; this group will contain Vorticeros and others, and will be distinguished from the Accela and the true Rhabdoccela by characters which will, we think, be better understood when that subject comes before us.
Molluscoida.
Test-Cells in Ascidian Ova.t—These cells, so characteristic of the ova of Tunicates, obtained their name from the belief that they * Morph. Jahrbuch, viii. (1882) pp. 73-83 (1 pl.).
t Zool. Anzeig., y. (1882) pp. 356-7.
492 SUMMARY OF CURRENT RESEARCHES RELATING TO
eventually formed the test enveloping the Ascidian. This view was shown to be erroneous, and Professor J. P. McMurrich now enunciates a new theory as to their function.*
The latest theories on the subject of parthenogenesis and of the nature of polar-globules are based on the assumption of the bisexual nature of the ovum, on account of which it is possible, and there is even a tendency, for a yolk to divide spontaneously. In most cases this is disadvantageous, and the formation of “ test-cells” is a means of guarding against the misfortune. On the exposure of the ova to sea-water or other abnormal condition a contraction of the yolk is brought about, and thereby a tension upon the nucleus, which, under the strain to which it is subjected, would divide, and so start the pro- cess of segmentation, were that strain not removed from it by the extrusion of the test-cells, whereby it is preserved intact until the proper stimulus in the shape of a spermatozoon excites it to a healthy and normal division.
This theory the author would also suggest as an explanation of the Excretkorper described by Hertwig and Oellacher as appearing in the ova of Amphibia and fish respectively, and also of the fatty globules described by the late Sir Wyville Thomson as occurring in the eggs of Comatula, to which structures test-cells bear no little resemblance.
Embryology of the Bryozoa.t—J. Barrois finds that the larva of a Bryozoon consists essentially of five principal parts; an aboral surface, the peripheral pait of the oral surface with the corona which is only the edge of it, the incubating pouch with the central part of the oral surface which is destined to form the intra-tentacular space, the intestine, and lastly, the rudiment of the polypite which already exists in the larva, where it forms a special organ, and takes more or less a part in the formation of the polypite.
In the Entoprocta these parts have most nearly the arrangement which is found in the adult; the aboral surface forms the integument of the larva, and the oral is retractile and can be withdrawn into the vestibule; the only change necessary to convert the larva into the adult is a rotation of the incubatory pouch and the intestine so as to bring them into relation with the rudiment of the polypite. In the Chilostomata there is developed, by the aboral growth of the corona, a pallial cavity ;—as the oral surface has here lost its retractile power, there must be a change in the position of the mantle before the larva can pass into the adult condition; here, therefore, there is a more marked metamorphosis. In the Ctenostomata the pallial cavity is enormous, and the cells of the corona are of very large size ; in the Cyclostomata there is no corona, but the oral surface continues to grow towards the aboral pole; and here, therefore, we have, in its most marked condition, the process which has become more and more
* Tn a previous paper he showed that the test-cells were produced by a con- traction of the yolk of the ovum, consequent on the action of various stimuli being formed, more or less distinctly according as the stimulus was capable of causing a greater or less contraction of the egg-contents.
+ Journ. Anat. et Physiol. (Robin) xviii. (1882) pp. 124-61 (1 pl.).
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 493
marked the further we are removed from the Entoprocta; in con- sequence of this the oral surface, which was at first entirely enclosed in the interior of a cavity (the vestibule) and covered over by the aboral surface, has gradually passed more and more to the exterior so as to form by itself the external integument and to drive the aboral surface into the interior of a cavity (the pallial cavity). In the most differentiated types of the Chilostomata and Ctenostomata we have seen that the aboral surface has been driven into the interior; not- withstanding this, the uppermost portion of this surface which forms the organ called the “ calotte” has always been seen to be projecting. In the Cyclostomata, however, the pallial cavity is always closed and covered over. Adding to these the Lophopoda, we may make the following table:
eaniaee Predominance of the aboral surface. Vestibule “oh cle a oO lg ak cla at its maximum. Intestine well developed.
Chilostomata and Gah erates of the corona. A pallial cavity. Ctenostomata (sac reduced) The intestine reduced to a mass of globules.
Cyclostomata and { Predominance of the oral surface. Pallial cavity Lophopoda (no sac). at its maximum. Intestine disappeared.
The author points out that from the point of view of larval forms only we seem to find an essential character in the antagonism of the two great cavities at the poles, and, when we carry this further, in the greater or less development of the mantle. It is according to the ex- tension of this last that we find one or other of the two surfaccs of the larva best developed; when there is a median extension of the mantle we find, moreover, that the intestine has partly disappeared ; while when it is at its maximum condition of extension there is no intestine at all. When we come to look at the matter in a more general way we see that this development of the mantle is not a matter of so great importance, inasmuch as every form of larva, no matter to what type it belongs, can always be referred to a common type, in which there is no mantle, in which the oral surface is always within the vestibule, and the aboral forms an integument. The history of the mantle is, then, only a history of a series of adaptive modifications.
Dealing with the mechanism of the metamorphosis, M. Barrois finds that if we try to construct a general type of adult Bryozoon we have to recognize (1) a foot corresponding to the oral pole, (2) the frontal surface, corresponding to that which answers to the oral, and (8) a tergal or anal surface. In the Entoprocta these can be easily made out, but in the Ectoprocta it is not always so distinct; in the forms where the zocecium is elongated we seem to have the primitive dis- position, in the flattened ones the tergal surface is increased in extent ; palingenesis is to be seen in the Ectoprocta, coonogenesis in the Entoprocta.
As the author regards the Bryozoa as belonging to the Vermes he notes that, with the exception of the Rotifera, the Bryozoa are the only Vermes in which a telostomiate condition is con- stantly manifested, either in the larval or in the adult condition; in other words, the division of the body is on the primitive or gastrula
494 SUMMARY OF CURRENT RESEARCHES RELATING TO
type, in which we see an oral and an aboral pole. A free-swimming Entoproctous larva is then formed on the same type as a Rotifer. Granting this, we must suppose that the Bryozoon is the result of a simple change of life; we know that these larvee often creep about on their oral surface. If this habit were to become permanent we should have in the change of habits a sufficient cause for the meta- morphosis ; the ciliary current carrying food to the mouth would, on passing it, abut against the anal extremity of the vestibule, and would gradually drive this back towards the superior extremity of the larva ; there would thus be produced the rotation, in which the digestive tube would be implicated. We may assume the earlier existence of a group of Probryozoa, free-swimming creatures, of a general Rotifer- form, only represented to-day by the larvee of some of the Entoprocta ; these on taking to creeping would have their form altered by a current of water. Her ,
New Adriatic Bryozoa.*—Dr. Piesser discovered in some material sent him from Rovigno in the Adriatic a Bryozoon, which he found difficult to determine on account of its having some of the characters of Gemellaria and some of Notamia, but he calls it Gemellaria, and considers that the definition of the genus must be widened to receive it.
It consists of rows of double cells back to back, and the aperture occupies most of the front. A zocecium does not spring immediately from the zoccium below as in Gemellaria loricata, but grows in the manner of Notamia bursaria; further, at the commencement of each branch instead of a pair of zocecia, there is only one, out of which a pair grow. There are radicle fibres which start from the back of a pair of cells and grow out independently, instead of uniting together and growing in a bundle down the dorsal surface of the colony.
The most perplexing point to Dr. Piesser was the occurrence of avicularia at the top of the zocecia, sometimes sessile and very minute, at others they are much larger and pedunculate. He thinks that these characters show that it is a connecting link between Gemellaria and Notamia, and if his interpretation is correct, about which opinions may perhaps vary, we may look upon this as another instance showing that the presence or absence of avicularia cannot often be relied upon for generic division. It may interest Dr. Piesser to know that although this curious species has not previously been described, yet it lives in the Bay of Naples, and has also been found from a locality outside the Mediterranean.
Arthropoda. a. Insecta.
Sensations of Sight conveyed by the Facet-eye.j—The experi- ments of Grenacher, Dor, and Exner, as to where the rays received by the compound eye of Insects ought to be and are concentrated, led to the most contradictory results, until Grenacher finally established the true view. Several points, however, as to the quality of the
* Neunter Jahresber. Westfalisch. Provinzial. Vereins fir Wiss. u. Kunst,
1881. + Abh. Senckenberg. Naturf. Ges. xii. (1880) pp. 35-123 (3 pls.).
ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 495
function of vision still required investigation. The close parallel with the Vertebrate eye which was attempted to be drawn, is quite fallacious. -Clearness of sight was said by Joh. Miller to coincide with long sight, and to be best exhibited in those eyes which have the greatest circumference—the greatest number of very small facets, large crystalline cones and dark pigment-mass; the nearer the object to the eye, he said, the clearer the view obtained of it.
Dr. J. Notthaft believes the size of the facets and the length of the radius of the curve of the eye to be the only factors in its structure which have an important bearing on this point. With regard to the effect produced by the presence of a number of receptive and refractive units—the units of the compound eye—he believes that the edges of the units and fields of sight are in contact ; when the curve of the eye is perfectly spherical the fields are approxi- mately polyhedric, like the facets, but when the curve is eccentric, distortion appears as magnification increases. The smallest angle of sight is constituted by the angular distances between the directions in which two neighbouring retinal elements look, or even between two such ocular elements regarded as wholes. A few examples may be given of the actual condition of things in some specific eyes :—
Difference a of istance at direction | yo, of Smallest Breadth Heading which the between F ei ‘S Angle of of Cn Sight-field two aces: Vision. Facets. Eve of a unit terminal of Eye = ent elements. mm. mm. Apis mellifica .. | 1042 | 54 |1° 56’ (or 0° 51)*| . -024 10-78 ‘| 67 cm. Formica rufa 51° 35 |1° 97° (worker)
Sphinx convolvuli | 67° 39 | 1° 43’ Acherontia atropos| 20° VS or Sai nor 0° 42) 5 e037 3:0 81 cm.
* Determined by calculation from the radius of the eye-sphere as compared with the breadth of a facet,
In spite of its large minimum angle of vision, the insect eye affords, under certain circumstances, as great an amount of distinct- ness of vision as the human eye, or even greater; for there is no minimum limit to the distance of vision, and objects near the eye are seen more clearly than anywhere else; the distinctness of vision diminishes as the square of the distance from the eye: these relations for the following insects are :—
Distance in mm. at which Amount of Clearness with a the Clearness Distance of =I. =0'1, 0. | 60 cm. Apis mellifica .. .. 1°35 177 3°36 0-000024
Sphing nerti 4. os 0°81 8°51 1:67 0:000035
496 SUMMARY OF CURRENT RESEARCHES RELATING TO
The indistinctness produced by distance has the effect of reducing the image of (e.g.) an Ailanthus leaf to an outline in which the different lobes are almost entirely merged together, and almost all the detail lost (cf. Figs. 88 and 89).
Exner’s view of the impression produced on the insect eye of the degree of rapidity of movement in any objects, viz. that it is inti-
Leaf of Ailanthus glandulosa, showing part taken by the different portions of the compound eye in viewing it.
Fic. 89.
Effect produced on the retina by the leaf thus viewed.
mately connected with the movement of the insect itself, must lead to absurd conclusions. Joh. Miiller’s view, that insects see objects only by means of the accurate perception of their illumination, is the most important point in the theory of mosaic sight (that of
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 497 compound eyes), and contains the key to its principle. Only those rays of light can affect the eye which fall on it in the radial direc- tion, i.e. in the direction of the long axes of the crystalline cones. Each retinula (retina of a single unit) receives a cylindrical bundle of light-rays from every visible object; exactly the same amount of an object is taken in, at whatever distance it is viewed, so the effect of motion is not produced by an increase in or reduction of the amount which is seen of a moving body.
The action of direct sunlight on insects is evidently, from their sensitiveness to it, of great importance to them. Seeing that the angle which the rays proceeding from the orb of the sun make on reaching the earth is on the average 32’, the smallest angle of vision for a unit of any insect’s eye being probably more than 10’ (39' is the lowest known to the author, viz. in an Aischna), the single image of the sun would be spread, at the most, over three unit-eyes, and, at the least, over one ; while the minute unit of the human eye, having an angular distance of 10" only, can take in ;1, of the sun’s disk, and thus the disk occupies in the retina a surface 192 units in diameter, and covering about 27,000 rods. The amount of light which can be received directly by the facetted eye from the sun is far less than that received by the human eye, in fact only from 5,1, to »7boo of the amount received in the latter case. The bearing of this * striking fact on the habits of the insect is difficult to see, but it may be asserted that the insect’s eye is thus well provided against the effects of a too intense light, while its sensibility to minute grades of illumination from terrestrial objects remains incontestably one of its most important properties. For by far the greater amount of the impinging light is absorbed by the epidermic structures, and owing to the spherical curvature of the eye, the rays which reach it coincide in direction with the optical axes of but a few of the units, and so but a small portion of the receptive nervous region is affected by them ; thus only the ;yy%so0 part of the sun’s disk is perceived by a single eye. This view is supported by Grenacher’s opinion that it is the median (i.e. direct and unrefracted) rays of the pencil which strike a facet, which are the most important. The perception of an object in all its dimensions and of its relation to surrounding bodies cannot be learned, as it is to some extent in our own case, during the short life of the insect. Some idea of the character of the insect’s vision may be gained from the observed fact that the natural impulse of the insect is to court the darkness (e.g. the lower sides of leaves, the shade of grass, &c.), in order to avoid observation; their well- known delight in brilliant illumination forming merely an episode in their life of caution. Probably they are to some extent subject to optical delusion; thus when the sun suddenly goes behind the clouds, the surrounding objects, before so brilliantly illuminated, would appear to be at a greater distance, owing to their loss of light. To ascertain the relations of objects with regard to the surrounding space is the most important function of this organ in these animals, and especially the relation of distance from the eye itself; these ends are attained by the comparatively large angular distance which
Ser. 2.—Vo.. II. 245
498 SUMMARY OF CURRENT RESEARCHES RELATING TO
the closely apposed elements present. The actual distinctness of the features of the object is less important here than with the human eye.
The reason for the existence of two forms of eye, simple and com- pound, in perfect insects, is that of separating the impressions of space and distance from those of distinct sight of the object (the latter end being attained by the stemmata or simple eyes). Four, on the whole strongly distinct, kinds of vision are differentiated in the animal kingdom :—
1. General sensation of the amount of light evolved in the environ-
ment and of the relative position of its source ; analogous to our sensa- tion of warmth, and exhibited only in small organisms with trans- parent outer coverings, and devoid of special portions of the body adapted for the function. 2. Sensitiveness to colour and shades of colour; general orientation as to environment, power of recognizing known objects—the “eye-spots” of Vermes, &c. 3. Information as to relative positions of surrounding objects affording guidance of movements, with slight amount of guidance as to characters of object—compound eye of Arthropoda. 4. The most clear and faith- ful perception of the objects, the images reversed by a lens which strongly refracts light. The contents of a plane are the subject of this kind of vision, which does not convey to the brain the distance or mutual relations of objects ; the plane may be either single, at a constant distance from the eye, or there may be several at distances which vary within certain limits, as when accommodation comes into play. In this case the third dimension, viz. depth or distance of objects, is obtained by movements made by the eye-bearing individual, relatively to the objects viewed, materially aided by the power of accommodation, when this is present; in its absence, as in the case of the stemmata of Arthropoda, this impression must be very feeble, since the moving animal obtains nothing but a disconnected series of images of the objects as they come one by one within the range of its organs, “The phylogeny of the compound eye is deducible from the fact of the acquired character of the movements of Arthropoda; as the faculty of motion became better developed, the organs of sight became modified, pari passu, into that form which successfully met the requirements of this mode of motion, in the manner above explained; the highest degree of development being naturally reached in the Insecta. All winged insects are thus provided, while but few of the wingless forms, such as larve, &c., have this form of eye.
The explanation of the peculiar character of the vision enjoyed by the compound eye lies in the lenticular curvature of the corneal facets, which do not act as Joh. Miller supposes, by magnifying the entering rays, but by admitting only those which are not likely to prove injurious; this appears to be shown by a comparison of the Insect with the Crustacean eye. The latter is remarkable (judging by the results obtained by Grenacher from Mysis) for its large angle of vision—3° 16’ in the instance taken—and is probably fitted to convey impressions from a distance not exceeding a metre. Taking into
ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 499
consideration the density and other light-absorbing properties of the medium in which the insects live, the amount of light received from an object must vary approximately as the cube of the distance of the source of light, hence the wide opening of the eye, admitting as much light as possible. The same effect as the perspective which is obtained in air is here produced by the indistinctness of objects, owing to the opacity of the medium, in proportion to their distance from the eye.
The structural causes for these differences are :—(1) the flatness or slight curvature of the Crustacean cornea, which does not hinder the entrance of any light which falls radially upon it, and (2) the strong convexity of the facets in insects, which causes refraction of the rays to a focus in front of the retina, and consequently a dimi- nution of the light which meets them; thus most of the hurtful rays —those whose direction is not exactly at right angles to the surface of the cornea—having entered the eye at its side, are again thrown to the side and absorbed by the walls and the pigment of the narrow tube, whose diameter at the apex only allows of the entrance of a small central pencil. With regard to the fate of strongly divergent rays, the refractive properties of the cornea would appear calculated to increase their brightness ; but this is the case only with objects at short distances, and has the advantage of giving distinct and recog- nizable images of objects within this range.
Nervous System of the Strepsiptera.*—The nervous system of the Strepsiptera has not been subject to any special researches. C. Th. von Siebold ¢ only states that these insects (Xenos vesparum) have one thoracic ganglion ; but he does not say anything about the number of cephalic and abdominal ganglia. HE. Brandt’s researches have been limited to four females and one male of Stylops melitite, and one female Xenos vesparum, preserved in spirit, the results of which are as follows :—
1. The cephalic division of the neryous system consists of the ganglion supra-cesophageum only, the ganglion infra esophageum being absent.
2. The thoracic division consists of a large ganglion containing five pairs of nuclei; it is divided into two parts, an anterior and smaller one, corresponding to the ganglion infra-esophageum and to the first thoracic ganglion of other insects, and a posterior and larger part, which corresponds to the other thoracic ganglia and to some abdominal ganglia. The interior division supplies nerves to the organs of the mouth (like the ganglion infra-cesophageum) and to the first pair of legs. The posterior and larger division of this ganglion supplies nerves to the second pair of wings, to the thorax, and to different segments of the abdomen.
3. The abdominal division of the nervous system consists of one abdominal ganglion, situated in the last third of the body. It is
* Abstract by the author of a memoir in Russian, St. Petersburg, 1878. Ann. and Mag. Nat. Hist., ix. (1882) pp. 456-7. ¢ Lehrb. d. vergl. Anat., i. (1848) p. 582. 24 2
500 SUMMARY OF CURRENT RESEARCHES RELATING TO
oval, and is connected with the thoracic ganglion by means of a long thin cord. From this ganglion spring three pairs of nerves, of which the first and second pairs branch out in the fifth and sixth segments of the abdomen, while the last pair branch out in the last segment of the abdomen and in the rectum.
This nervous system is as curious as that of some Coleoptera (Rhizotrogus solstitialis, Serica brunnea) and some Hemiptera (Hydro- metra lacustris), as it has no ganglion infra-cesophagewm.
Insects which injure Books.—Professor A. Liversidge, of Sydney, sends us some specimens of Lepisma saccharina, and points out that “in Blades’ ‘ Enemies of Books, 3rd ed. (1881) pp. 61-3, he refers to the description of a book-worm in Hooke’s ‘ Micrographia’ (1665), and rather makes fun of the figure and description there given— ‘certainly R. Hooke, Fellow of the Royal Society, drew somewhat upon his imagination here, having apparently evolved both engraving and description from his inner consciousness.’ -
People living in New South Wales and other of the warmer parts of Australia can, however, bear testimony to the accuracy of Hooke’s statements and drawing. The insect figured in the ‘ Micro- graphia’ abounds here amongst books and papers, and is wonderfully destructive to them. It does not do so much harm to books as it does to loose papers, maps, labels, &c., as it cannot well get in between the closely pressed leaves of a book, and it is on this account that the loose edges of piles of MS., bundles of letters, &c., suffer so much more than the central portions; writing paper, too, probably contains much more attractive matter in the way of size, &c.
With this I enclose some scraps of paper showing the ravages of the insect (Lepisma), and also some of the ‘silver fish’ themselves, by which name they are commonly known here and also in India, whence I understand the name ‘silver fish’ originated.
The destruction of labels is a very serious one, as the identity of a specimen may very soon be lost. The labels enclosed have only been written about fifteen months, and some hundreds have thus been rendered totally useless. In future it will be necessary to saturate the labels with a poison, such as corrosive sublimate.
At times I have thought that, perhaps, the ‘silver fish’ instead of doing harm may be doing good—for wherever they are found we are likely to find pseudo-scorpions (chelifer), and it may be that the former prey upon the latter; though I think not.”
Formation of Galls.*—M. W. Beyerinck finds that “ galligenesis ” affects a portion of the vegetal tissue, which becomes altered in character, and may then be known as galliplastema ; the galligenetic influence is due to the larve and not to the hymenopterous parent. The phenomenon of formation of the galls is absolutely indepen- dent of the lesions which the deposition of the eggs causes in the living tissues of the plant. Direct contact between the animal and the plant is not necessary for the production of the galliplastema ; there may be a layer of dead cells, or even the covering of the egg
* Rev. Internat. Sci. Biol., ix. (1882) pp. 373-4.
ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 501
between them, and this intermediate space may be greater than the diameter of the larva. In the cases in which the animal that produced the gall had originally only one point of contact with the galli- plastema, the further inclusion of the larva is due to an annular investment of the plastema, which increases in extent and becomes folded over it. A temporary contact on the part of the larva does not produce a gall. The larve are fed by the development in the gall of a tissue the cells of which have thin walls and contents rich in oil and albumen. In their anatomical structure many of the galls have characters which appear to be completely foreign to the organization of the plants that nourish them.
y. Arachnida.
Anatomy of Phalangida.*—Dr. R. Réssler finds that the digestive system consists of three portions, of which the spacious midgut is provided with a large number of ceca; the sucking action is pro- duced by a layer of strong transversely-striated circular muscles, which is only continued on to the more anterior portion of the succeeding oesophagus; the lumen of this latter region is almost completely filled up by six longitudinal folds, consisting of a trans- parent cuticle with a subjacent layer; the cells of the salivary glands may be seen, in section, to form one layer and two smaller complexes below the cesophagus; the secretion has an acid reaction. All the thirty ceca are without a muscular investment, and consist only of a thin fat-layer, a tunica propria, and an epithelium; the Malpighian vessels are represented by two tubes, forming a loop, which are placed near the median ventricle, and open not into the intestinal tract, but into two sacs on the ventral surface of the animal.
The genital organs of the two sexes are referable to a common plan, consisting as they do of an unpaired germinal gland, semicircular in form, lying freely in the body-cavity, and only surrounded by a rich supply of trachez ; there is connected with this gland a paired efferent apparatus, which however becomes united into an unpaired piece, and finally opens to the exterior in the median ventral line, between the cephalothorax and the abdomen. Connected with the terminal portion is a copulatory organ, into the anterior portion of which there open a pair of accessory gland-organs ; the penis is rod-shaped, the ovipositor is cylindrical, and the vagina has a seminal pouch on either side. The testis is a simple tubular organ about 4 mm. long and 0:4 mm. wide; the spermatozoa are large, biconvex, rounded cells, with a lens-shaped nucleus ; the vasa efferentia commence as two fine canals, and soon form a close coil; the cells of the lumen become commingled with the products of the testis; the propulsion-organ has a thick muscular layer, the fibres of which are transversely striated, and there is a thick chitinous layer secreted by the epithelium; the lumen of the ductus ejaculatorius is narrow; chitin is also to be found in the penis. The ovary is horseshoe-shaped, invested by transverse and longitudinal muscular fibres, and when mature is beset with a
* Zeitschr. f. wiss. Zool., xxxvi. (1882) pp. 671-702 (2 pls.).
502 SUMMARY OF CURRENT RESEARCHES RELATING TO
large number of follicles of variousages. These, which may be looked upon as evaginations of the tunica propria, all contain an egg, more or less developed, but the ova are always of small size until they make their way into the uterus, which then attain their full size and development. In the immature female the uterus 1s only apparent as a slight outpushing of the oviduct, but at the period of maturity it becomes turgescent, swells out, and occupies a large portion of the body-cavity ; itis provided with a powerful layer of circular muscular fibres, and its inner surface is lined with cells, similar in character to those of the vas deferens. The terminal portion of the vagina is surrounded by a system of chitinous rings; the ovipositor, like the penis, is surrounded by two sheaths, which are essentially of the same structure in all the species.
The two glands at the lateral margins of the cephalothorax have been regarded by Loman as stink-glands; the author finds that in Opilio albescens there is an aromatic odour, which he ascribes to these organs.
Scent-glands of the Scorpion-spiders (Thelyphonus).*—The re- markable Arachnidan genus T’helyphonus is confined in its distribution to South America and Southern Asia and their islands. Of its internal anatomy nothing but the nervous system is known. The French zoologist Lucas states that the Thelyphom are called Vinai- griers by the inhabitants of Martinique, on account of the strong vinegary odour which they emit when touched or handled. Stoliczka, who examined living specimens of one of the Indian species, states that a peculiar but inodorous fluid issues from two internal pyloric (!) appendages. These Arachnids, according to Lucas, live in damp places under stones on the ground. Stoliezka and Mr. Peal found them beneath the bark of decayed trees in groups.
Mr. J. Wood-Mason, who has undertaken an investigation of their anatomy, was only able to obtain specimens for dissection during the heaviest rain, when all vegetation and the ground is saturated with water, and the animals come forth from their holes in the rocks. He found that death quickly followed their removal from their humid haunts, air saturated with moisture being apparently necessary for the due performance of their respiratory functions. All the specimens he met with emitted, when touched, a most powerful and lasting odour, exactly like that of a highly concentrated essence of pears, which when deeply inspired had all the characteristic smell and pun- gency of strong acetic acid. This odour did not emanate from the general surface of the body, but proceeded from a pellucid fluid which exudes from the neighbourhood of the anus and is secreted by special glands. These are paired and tubular organs of huge size, extending from the nineteenth somite of the body (on which they open by two minute valvular apertures placed at the sides of the anus) to the front end of the thirteenth in the male, but to the middle of the eleventh in the female (whose glands are consequently the larger), and being, with the exception of the voluminous liver, the most conspicuous of the viscera. They are two subpellucid bags, shaped somewhat like
* Proc, Asiatic Soc. Bengal, 1882, pp. 59-60.
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 503
an Indian club, striped longitudinally with white, and filled to dis- tension with a thin clear fluid. They are not quite equal, nor are they placed symmetrically in the body-cavity, but the one or the other lies between the nervous chain and the ventral body-wall in the middle line between the two rows of vertical muscles, and the other between the row of muscles and the lateral wall of the side of the body to which it properly belongs. They apparently consist of a strong and structureless basement membrane, invested externally by a layer of delicate striped muscular fibres arranged circularly, and of an inner membrane; the walls of the short (1 mm. long) ducts are transversely thickened so as to resemble the trachew of insects; the granular tissue is arranged between the two membranes in longi- tudinal plated stripes, so as to permit of the expansion of the lumen of the tubular organ in a receptacle or bladder for the storing up for use of the secreted fluid, to which apparent arrangement of the granular substance the striped appearance of the organs is due.
The secretion doubtless serves to protect the animal from attack, and it is interesting to find that the female in this, as in so many other animals which are similarly protected by their offensive odour, is (as being for obvious reasons the more important sex) more perfectly protected than the male by having, not indeed, so far as could be detected, a stronger and ranker, and therefore more disagree- able scent, as in many insects, but larger scent-secreting glands. Another point of interest brought out by this investigation is that the two glands exhibit a tendency to coalesce and form a single unpaired median organ, the two being always unequal and occasionally partially united and the one in the middle line invariably the larger.
These structures seem to belong rather to the category of excre- tory organs than to be highly developed skin-glands; and they are probably homologous with the silk-glands of other Arachnida and of Insects, with the green-gland of the Crayfish, and with the segmental organs of Worms and Peripatus.
5, Crustacea.
Classification of the Brain of Crustacea.*—Dr. A. S. Packard gives the following provisional grouping of the brain of Crustacea, which he considers to be justified by known facts, although excepting the brains of Decapoda and Limulus, no special histological work has been accomplished. The terms archi-cerebrum and syn-cerebrum have been proposed by Professor Lankester, the first to designate the simple worm-like brain of Apus, and the second the composite brain of the Decapoda, &e.
Decapoda. Tetradecapoda.
Syn-cerebrum ( Phyllocarida. Cladocera. Entomostraca. Phyllopoda.
Archi-cerebrum {Metta (Limulus). Cirripedia ?
* Amer. Natural., xvi. (1882) pp. 588-9.
504 SUMMARY OF CURRENT RESEARCHES RELATING TO
The syn-cerebrum of the Tetradecapoda, Amphipoda, and Isopoda, judging by Leydig’s figures and his own observations on that of Idotea and Lerolis,is built on a different plan from that of the Deca- poda. The syn-cerebrum of the Phyllocarida is somewhat like that of the Cladocera and Copepoda (Calanidz) ; being essentially different from that of the majority of the Malacostracous Crustacea. ‘The Copepodous brain is an unstable, variable organ, but on the whole belongs to a different category from the syn-cerebrum of other Neocarida.
We have then, probably two types of archi-cerebra, and three types of syn-cerebra among existing Crustacea.
Unpaired Eye of Crustacea.*—In most Crustacea, besides the two compound eyes (fused together in the Cladocera), there exists an unpaired median eye. It exists alone in most of the Copepoda, and in all naupliiform larve. Wherever the two kinds coexist in the adult but not in the newly hatched larva, the unpaired eye is the first formed, and must therefore be regarded as the primitive eye of the Crustacea. By thin sections of Cyclops and Diaptomus, Mr. M. M. Hartog has ascertained that this organ is of a much more complicated composition than had been supposed. The pigmented mass is, so to speak, structureless; the colouring-granules in it are placed at the surface contiguous to the “crystalline spheres.” Hach sphere is com- posed of radiating elements, the inner ends of which are applied against the pigmented mass, while the peripheral segments contain a nucleus. The eye is situated upon the terminal process of the brain, from which the optic nerves originate, one for each sphere; the nerve, instead of penetrating into the pigmented mass, skirts the outer surface of the crystalline sphere, and penetrates it directly not far from its hinder margin. The author has also found in the Phyllopoda a perfect analogy of structure with that just described in the Copepoda, and therefore concludes that the unpaired eye in all the Crustacea that possess it, is composed of three simple eyes, placed anterior to the brain, with reversed optical bacilli, receiving conductive fibres of the optic nerve upon their outer margin, and brought so close together that their pigmented or choroid layers are combined in a single mass.
A nearly identical structure may be detected in the Chetognatha, which have the triple eye of the Crustacea; but, instead of being median and unpaired, it is repeated on the two sides of the head ; certain Planarians, Dendrocelum lacteum for example, have two paired eyes, which, according to Carriére, have the structure adopted by the author for one of the simple eyes united in the median eye of the Crustacea.
It is probable that the eye of the Chetognatha and Crustacea is to be referred back to the type of the Planarians, but that the two former groups have no direct relationship between them.
Blood of the Crustacea.t—G. Pouchet is reported to find that the differences seen in the blood of these animals is not, as Wharton
* Comptes Rendus, xciv. (1882) pp. 1430-2. + Journ. Anat. et Physiol. (Robin) xviii. (1882) pp. 202-4.
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 505
Jones thought, due to differences in the time of year. Their blood is remarkable for the large quantity of sea-salt which it contains, a drop from a Maia laid on a glass slide and dried giving a large number of crystals. Coagulation takes place very rapidly. Notwithstanding the great variation in form of the leucocytes, it is possible to re- cognize a common type; a large number have the form of young blood-corpuscles of oviparous vertebrates; as they grow older they present a number of granulations, and, as their nucleus is then often small or altogether lost, the author is of opinion that the granular condition represents the last stage in the development of these bodies. The form and the size appear to differ considerably as we pass from one species to another; the form, which is always ovoid, appears to be permanent so long as the blood is retained within the circulatory cavities; as an example of this we may cite the case of Palemon, where the leucocytes found in the lateral lobes of the telson did not, during a long period of examination, exhibit any amceboid changes.
Pyloric Ampulle of Podophthalmate Crustacea. *—F. Mocquard describes the ampulle as forming the floor of the median part of the pyloric duct; in most cases they may be compared to two demi- cylinders placed side by side, with the cavity upwards. The surfaces are not, however, regularly cylindrical, for they are rounded and truncated obliquely behind. Their inner edges unite to form a pro- jecting longitudinal—interampullar—fold; from their cavities and from the sides of the fold there arise a large number of parallel longitudinal crests, on the free edges of which there are rows of ex- tremely fine sete; from this arrangement there results a considerable number of small prismatic canaliculi, directed from before backwards ; the free edge of the posterior portion of each of these ampullar crests is continued into a large seta, which is directed backwards and carries extremely fine sete. A remarkable point in this arrangement is that very slight differences are found even when the Stomapoda are com- pared with the Decapoda. Similar ampulle are to be seen in the larvee (and doubtless also in other forms) even when there is no gastric armature; while further, though absent in the Mysis, they are to be found in the Mysis-stage.
We never find any appreciable amount of food in the ampullar cavities, and their functions would appear to be this: while the nutritious matters which are difficult of digestion remain in the superior portion of the pyloric duct, the more finely divided par- ticles make their way between the interampullar fold and the side- wall of the pylorus along a line parallel to, but in a contrary direction to that of the sete; they are thus broken and brought into a sufficiently fine state to enable them to penetrate into the canaliculi, whence they pass backwards in a longitudinal direction. In support of this view, the author directs attention to the fact that the excretory ducts of the so-called liver empty their products not far from the posterior orifice of the canaliculi, where the alimentary matters and this secretion would therefore be brought into intimate contact.
* Comptes Rendus, xciv, (1882) pp. 1208-11.
506 SUMMARY OF CURRENT RESEARCHES RELATING TO
Heterogeny of Daphnia.*—C. L. Herrick, in the course of re- searches upon the development of Daphnia Schaefferi (= magna), observed several interesting facts.
The embryo, before leaving the egg, in both summer and winter forms, is furnished with palpi on the base of the second antennz, and a long appendage from the dorsal region of the shell. The former, though quite large in the embryo, is later nearly atrophied, remaining during life, however, as a wart-like process with two rather small spines. The latter is curved beneath the body, lying between the valves of the shell. After the escape of the animal from the egg this organ becomes the dorsal spine, and seems to serve as an aid to the complete moulting of the walls of the brood-cavity, with the first development of which the spine seems also to stand in intimate relation.
It is worthy of remark that not only the mature animal, after long confinement in aquaria, becomes smaller and stouter, and in other peculiarities resembles the smaller spined species of Daphnia, but that the young retain the dorsal spine and the shorter form till in a sexually mature condition, when in confinement. This fact, and the discovery of Dr. Birge, that the spine upon the head of another species of Daphnia is also an embryonic organ, serve to call attention to the systematic position of this genus. It would therefore appear that the species Schaefferi is the culmination of a cycle of forms, among which are to be counted more or fewer of the species described as distinct.
Daphnia thus furnishes another example of so-called “ Heterogeny.”
Notodelphyide.j—W. Giesbrecht describes the female repro- ductive organs of these parasitic Copepoda. ‘The ovarian tubes are completely differentiated before the last ecdysis, when they present the following features; there is a structureless tunica propria lined by a simple epithelium, the cells of which are as broad as high. As changes occur, this epithelium becomes separated off from the wall of the tube; the process commences at the anterior end, and gradually passes backwards, so that in a series of sections the anterior ones are filled with the separated cells, while the lumen of the hinder ones is still open and the wall invested by epithelium; the cells do not break off separately but in longitudinal rows. When this process has come to an end, the walls of the tube are formed by a distinct membrane, which is lined by a layer of protoplasm; at first the nuclei in this latter are at some distance from one another, but they soon come to form groups of two to six. The tube, therefore, first had the function of a germ-producer, and may be called the ovary, while, later, it serves as an oviduct, and affords nutriment to the growing ovarian cells. Owing to their coming off in longitudinal rows, the ova now lying in the tube are arranged in cords of a cylindrical form, each of which may have as many as one hundred eggs; there is no investing membrane to these ovarian cords. A little later the
* Zool. Anzeig., v. (1882) pp. 234-5. + MT. Zool. Stat. Neapel, iii. (1882) pp. 293-372 (8 pls.).
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 507
separate cells begin to be distinguished from their neighbours; many of them increase in size by the growth of their peripheral portion, and the internal contents of these do not therefore become altered in character. Others develope within themselves fatty bodies. Under the influence of the growing ova the paired portions of the ovarian tubes increase greatly in diameter, and soon after this the eggs make their way into the maternal cavity, where they pass through the stages of development prior to the Nauplius condition. The dorsal folds are chiefly formed of a connective tissue, which consists largely of membranous elements and partly of spindle-shaped fibres, which may be regarded as muscle-cells; in addition to these there are rounded fibres, which extend from one surface to the other. Rounded or ellipsoidal bodies are to be found lying in the meshes of the tissue, filled by a very regularly arranged polyhedral meshwork of very delicate membranes. A number of fatty cords traverse the appendage in a radial manner; these are processes of the fat-body which is so frequently found in parasitic Crustacea and are here particularly well developed. The investing membrane is a continua- tion of the general chitinous covering of the body, though it is here more delicate than in other regions. As there is in all essential points the very closest agreement between the structure of these folds and that of the other parts of the body, it would be better to speak of them as processes of the body-cavity, than as dermal folds. The specially modified portion which serves as a brood-pouch has its internal lamella formed by a specially thick chitinous membrane, and is at first so folded as to allow of the increase in size of the cavity which becomes necessary later on.
Some of the habits of these forms are treated of in detail, and it is pointed out that the first copulation commences before the final ecdysis of the female, but the attachment of the spermatophores only becomes completed after the ecdysis; in this action of the male, the appendages, and specially the fourth or fifth pair of feet, take part. Various males may fertilize the same female who remains completely passive during the whole act. ‘The reason of this apparently prema- ture copulation is considered, and the suggestion is made that it is an arrangement derived from an earlier condition in which the female did not pass through the last ecdysis.
The succeeding acts of oviposition and delivery are described ; they are repeated at regular and constant intervals, whereas the later acts of copulation are not so definitely arranged. A female who has just deposited her ova, has a thin, faintly-coloured, hardly detectable ovarian tube; five days afterwards this is again filled, and the red eye-spots of the embryos in the brood-cavity can be made out. After ten days from oviposition, the embryos are ready for extrusion, and again the ovarian tube will be found full; for about two and a half days the brood-pouch remains empty.
The author does not look upon the development of the fat-body as an arrangement which owes its origin to the struggle for existence, but as a passive necessary result of the parasitic habits of these animals; the assimilated nutriment which the free-living forms use
508 SUMMARY OF CURRENT RESEARCHES RELATING TO
up owing to their activity, has no use in an organism which lives a parasitic life; and the physiological process is therefore completely similar to that which obtains in fattened cattle.
' The earlier part of the paper is taken up by (1) an account of the presence of these forms in certain Ascidians, the author only finding them in Phallusia mentula, and P. mammillata, where they are far from being the only guests; (2) a description of their external form ; and (8) a systematic account of the species, which are arranged under the genus Doropygus, with as subgenera, Doropygus and Notopterophorus. Seven species appear to be known.
Organization of Trilobites.*—The veteran H. Milne-Edwards, in discussing the results of the researches of Mr. Walcott,f concludes that the alliance, on which he long ago insisted, between the 'Trilo- bites, Isopoda, and Phyllopoda, is strengthened rather than weakened by these studies; he cannot believe that they were representatives of the Arachnidan type from which the Limuli appear to have been de- rived, and he thinks that a group composed of Trilobites, Limul, and Eurypterina would be altogether artificial and inadmissible into a natural zoological classification.
It is pointed out that although there is, at first sight, a very con- siderable resemblance between young Limuli and young Trilobites, yet that the latter soon become provided with thoracic segments, and, to cite characters of less importance, they tend to become ornamented with those long spiniform prolongations, the presence of which is so characteristic not only of Zoex, but of many adult Macroura.
If we examine the respiratory organs of the Trilobites, we find them to differ much more from the Limuli than they do from the Branchiopoda or the Hedriophthalmata. The principal differences between the external structure of a Limulus and of a Phyllopod or an Isopod are to be found in the relations of the mouth to the appendi- cular system, and the mode of division of labour between the different parts. In the Limuli we find two distinct groups: one forms a masticatory, prehensile, and ambulatory system, at the centre of which we find the mouth; the other, the respiratory apparatus, is situated more posteriorly, and presents none of the characteristic forms of any Arthropod walking limb; no known existing animal has a similar structure, and no one of the recently observed facts leads us to see any close resemblance to them in the Trilobites. Prof. Milne- Edwards has now no doubt as to the existence of a long series of post- cephalic limbs in the Trilobites, and the characters of these appear to him to present a certain resemblance to those of Apus ; it is possible that they were almost altogether homomorphous and natatory rather than ambulatory. It is pointed out that we have an erroneous idea of the essential characters of the appendicular apparatus of the Phyllo- poda, if we imagine that they are always entirely soft and membranous ; in Apus the coxopodite and some of the succeeding joints of the internal ramus are thick and firm, and we can imagine that under the
* Ann. Sci. Nat. (Zool.) xii. (1881) Art. No. 3, 33 pp. (8 pls.). + See this Journal, i. (1881) p. 736
ZOOLOGY AND BOTANY, MIOROSCOPY, ETC. 509
effects of fossilization nothing but the parts of this internal ramus might be left to be preserved.
Vermes.
Chemical Composition of Tubes of Onuphis.* — Professor O. Schmiedeberg finds that the tubes of this Annelid consist not only of a mixture of albuminoid substance and of potassium and sodium, but of a special body (onuphin) made up of organic and inorganic bodies ; the presence of this body may be explained by the view of Ehlers that the tube is a secretion of the separate segments of the animal, a view which is based on the plentifulness of the secretion of certain glands. The question of the origin of the chemical com- ponents is considered by a reference to the quantitative analyses of various sea-waters, and it is pointed out that the striated structure of the tube is due to the different layers being separated by an albu- minoid substance. The question of their food is not yet satisfactorily settled, nor have we yet the necessary knowledge of the exact consti- tution of onuphin.
Nematoid Hematozoon from a Camel.tj—Dr. T. R. Lewis, recalling the fact that the occasional presence of nematoid organisms in the blood of various animals has long been ascertained, and that ten years ago he had shown that in India a somewhat similar condition was observable in man (associated with certain forms of grave disease), points out that an important contribution to our knowledge of the hematozoa of the lower animals has been made by Dr. G. Evans, the head of the veterinary department of Madras, who, whilst making a post-mortem examination of a camel, found that the blood of the animal swarmed with the brood of a nematoid parasite resembling the hematozoon of man, Dr. Evans found, further, that the parental form existed in the lungs, the pulmonary arteries of which were plugged by tangled masses of the thread-like parasites. They were also found in the mesentery.
A comparison of these hematozoa with those found in man shows that, whereas the embryonal forms of both kinds are indistinguish- able under the Microscope, nevertheless the mature form as met with in the camel differs, both as to size and structure, from the only male and female specimen of the mature form met with in man which has hitherto been obtained in India; and so far as Dr. Lewis is aware, this hematozoon of the camel differs from any hitherto described parasite. Should further inquiry confirm the supposition that the parasite is new to science, he proposed that it should be called Filaria Evansi. A preliminary description is given of both male and female forms.
Development of Marine Planaria.{— Among other important points, Prof. E.Selenka here discusses the affinities of the Planaria to the Ctenophora and the Nemertinea. We find a considerable
* MT. Zool. Stat. Neapel, iii. (1882) pp. 373-92. + Proc. Asiatic Soc. Bengal, 1882, pp. 63-4. + Zool. Studien, ii. (1881) 44 pp. (7 pls.).
510 SUMMARY OF CURRENT RESEARCHES RELATING TO
though not complete similarity in developmental history between the Planaria and the Ctenophora. In both cases (1) the endoderm arises as four large pale cells, and this layer gives rise to a quadri-radiate enteron, which is permanent in the Ctenophora, but modified in the Planaria. (2) The gastrula arises by epiboly, and the blastopore and permanent mouth are coincident in position. (3) Stinging cells are to be observed in both. (4) The embryo has in both a predominantly radial (symmetrical) arrangement, but in both this is later on more or less completely modified into a bilateral sym- metry. On the other hand—(1) There does not seem to be in the Planaria more than a feeble indication of an aboral sensory capsule with otoliths, such as seen in the Ctenophora. (2) A complete in- vestment of cilia is but rarely found in the Ctenophora, e.g. embryo of Eucharis. (3) Nothing comparable to the eight ctenophoral plates of the Ctenophora can be detected in the Planaria. The relations of the Ctenophora and the Planaria are hardly to be doubted.
Turning to the Nemertinea, we find that in these the quadri- radiate symmetrical cleavage is confined to the very earliest stages, the endodermal cells are small, and there is no kind of communi- cation between the enteron and the celom; on the other hand, stinging organs are to be found on the proboscis, the blastopore and permanent mouth are coincident, and, in fine, the Planaria in some cases present intermediate conditions between the Nemertinea and the Ctenophora.
The chief objects of the author’s investigations have been Lepto- plana tremellaris, L. alcinoi, Eurylepta cristata, and Thysanozoon diesingi.
Eyes of Planarians.*—Former investigations { having done little more than elucidate the ewternal characters of these organs, J. Carriére hag applied himself to determining their intimate structure, especially that of the nervous elements. The method employed was preserva- tion by Lang’s method, viz. a liquid composed of chloride of mercury 5 parts, glacial acetic acid 5 parts, water 100 parts; after twenty minutes or half an hour the specimen was transferred to alcohol of 70 per cent.; sectious were made and stained with picrocarmine.
In Planaria polychroa there is an optic ganglion immediately in con- tact with each eye, on its outer side, and consisting of an external layer of nuclei resembling those of the cerebral ganglion, and about -008 mm. in length, enclosing a larger mass of fine fibres. Among these fibres are some which are strongly refractive, and pass in straight lines inwards, swelling ‘out, and ending in rather broad knobs within the pigmented hollow (“ pigment-cup’’), and which they probably fully occupy in life. The pigment mass consists of small globules, varying in size from +255 to e457 mm. in diameter. The eye of Dendrocelum lacteum is double; the pigment-cup is single, but has two posterior openings instead of one. The eye of Leptoplana tremellaris, described by Keferstein in very different terms, appears, however, to agree -
* Arch. Mikr. Anat., xx. (1881) pp. 160-74 (1 pl.). + See this Journal, i. (1881) p. 605.
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 511
essentially with those just described. Study of pathological and abnormal specimens appears to show that the large eyes of the two former Planarians have been developed from aggregations of small ones, each consisting of a nervous cell invested by pigment; such eyes, in fact, appear in some cases as accessory appendages to the main organs. Polycelis nigra has the margin of the anterior end of the body beset with pigmented ocular organs, which are often united together in twos or threes. Their structure differs, however, very widely from that of the eyes of Planaria polychroa. Each eye consists of a homogeneous sphere, invested on its posterior side with a pigment- cup of distinct granules, which is open in front; in contact with the back of the latter organ is a large trausparent hemispherical nucleated cell. The eye appears to be surrounded by ganglion-cells whose nuclei are distinct, but whose exact relations to the eye have not been made out.
Development of the Orthonectida.*—C. Julin, although agreeing with Metschnikoff in regarding Rhopalura ophiocome and Intoshia gigas as the male and female forms of the same species, has never been able to detect them both in the same Ophiurid. When an Amphiura squamata infested with males is opened there escape hundreds of individuals in different stages of development. After the first cleavage one of the blastomeres is very much larger than the other, and is more opaque; this is the ectodermic while the other is the endodermic globule. The former gives rise to as many as fourteen cells before the latter divides at all; thus there arises a condition of epiboly, where the endodermic cell is ovoid in form and has its long axis parallel to that of the embryo; the enclosed cell now undergoes division, and gives rise to a small cell at either end; one of these occupies the orifice of the blastopore. These small cells now divide into six and four respectively, and the ectoderm becomes completely ciliated; as the embryo elongates the small cells increase in length, and becoming fusiform completely envelope the central endodermal mass; in the adult they form the longitudinally striated fibres. Meantime, the central endodermic cell has divided into a large number of smaller cells, each of which contains a fragment of the primitive endodermal nucleus; each of these gives rise to a sper- matozoon. Although the primordial muscular cells have been given off from it, the central cell still possesses a true membrane, which persists during the whole life of the animal and forms a pouch for the contained spermatozoa.
While the males are free the embryonic females are connected together by a granular mass (the sporocysts of Giard, plasmodial tubes of Metschnikoff). There would appear to be very great difficulties in the study of their earlier stages owing to this mode of connection. But here also there is ectodermic epiboly, though the endodermic cell divides earlier to give rise to a mass of polyhedral cells, sur- rounded by a layer of cubical non-ciliated cells. Later on these peripheral cells become cylindrical, and still later they form a com-
* Bull. Sci. Dép. Nord, iv. (1881) pp. 309-18.
51D SUMMARY OF CURRENT RESEARCHES RELATING TO
plete but very delicate layer of fibrils, apparently comparable to the muscular layer found in the corresponding position in the male. The central polyhedral cells give rise to ova. There is, therefore, an essential agreement between the developmental processes of the male and female.
The male products escape, by the rupturing of their investing wall, into the muscular layer, where a passage is found for them ; the ectoderm undergoes change and atrophy, and the spermatozoa make their way out. The ectoderm of the female breaks off at a non- ciliated region at the anterior end, and thus the ova escape. There is another female form which seems to divide into two or three pieces, and which is distinguished by being flattened, and not cylindrical.
The females, when mature, appear to leave one host to swim in the water and to enter another, and there is some reason to believe that the cylindrical forms give rise to the males, while the flattened forms would seem to be the parents of the females. These latter possibly arise by parthenogenesis.
The author promises a fuller paper, in which he will give more details and full reasons for his belief that the Orthonectida belong to Van Beneden’s group of the Mesozoa, and he concludes with an ob- jection to the application of the terms metamere or segment to these creatures, as the segmentation is superficial, affecting only the ecto- derm, and the number of segments does, it is allowed, vary.
Eyes of Rotifers.—Referring to his note read at the June meeting of the Society,* Mr. Badcock writes (July 17) :—“ Yesterday for the first time I discovered eyes in a group of adult Floscularia cornuta, and saw them again very distinctly in Stephanoceros eichhornii. It seems to me desirable to put on record the fact that the eyes are found in the adult forms of Melicerta ringens, M. tyro or tubicularia, Floscularia cornuta, and Stephanoceros eichhornii, in all of which the eye is ignored in the usual descriptions and drawings. ‘The eyes are not readily seen, but I have had some very fine specimens, and may be able eventually to demonstrate their existence in all the forms in which they were supposed to have been lost.”
Echinodermata.
Anatomy of Holothurians.j—E. Jourdan finds in the connective tissue of the integument of these Echinodermata elements forming a plexus; they are coloured grey by osmic acid, are rarely isolated, and are very often united into bundles. They arise from nerves which penetrate into and extend through the skin. The fibres of this nervous plexus are accompanied by nuclei, which are chiefly found at the points of interlacement of the fibres. These fibres are very fine, slightly varicose, and accompanied by fatty granu- lations. ‘The nervous centres consist of fibres and cells. The latter are frequently, though not always, unipolar.
The muscular elements of Holothurians are made up of fibres
* See this Journal, post, Proceedings. + Comptes Rendus, xciv. (1882) pp. 1206-8.
ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 513
which are remarkable for the irregularity of their form and their length. They are always provided with one or more nuclei, which are always lateral in position, large in size, and attached to the fibre by a delicate sarcolemma. The walls of the Polian vesicles consist of an outer layer of flattened cells, which recall the endothelial lym- phatic cell; a layer of connective tissue in which the fibres are longi- tudinal ; a layer of circular muscular fibres, which are very long, and have the appearance, when extended, of elastic fibres, in a state of contraction. They present a number of swellings. Within this there is a layer of epithelial cells.
Hybridization of Echinoidea.*—R. Koehler finds that, at Mar- seilles, the genital glands of most species are mature in March or April. In making experiments, however, it is necessary to assure oneself by microscopical examination that the elements are ripe, and with the crossing experiments it is right to fecundate by their own spermatozoa the ova of the species treated. When the ova of Strongylocentrotus lividus were fecundated by Spherechinus granu- laris, the Pluteus was regularly and perfectly developed. The same happened when the male was Psammechinus pulchellus. When the male was Dorocidaris papillata, the eggs did not pass beyond the blastula-stage, but the spermatozoa used were here somewhat inactive. A female Strongylocentrotus is not always fecundated by a male Spatangus purpureus. Sometimes, however, even the gastrula-stage may be reached.
Other examples are given, and the whole shows that cross fecundation is possible, within very wide limits, among the species of the Echinoidea; while the Pluteus derived from the crossing of two regular Echinoids may not differ much from the normal Pluteus of the female in the experiment, there are certainly well-marked differences between the legitimate Pluteus of a Spatangus and the hybrid Pluteus of that and Psammechinus. While the ova of one species may be fertilized by another, the reverse may not hold true.
Variation in Asterias glacialis.|—Professor Jeffrey Bell describes “ six sets at least” of forms of</