f ek oO 8 A Raw eae saa te . et) 6 ee ee bee . rr” i. ro ae ae ee oN tale Leda 4 rere a el oe Gel 4 act te Hh a9 Dy tye boty Opes OF oF Bee eS 4 wr Aa 4 4det ba 4! OD eu wie wee we ee ont ete 4d AME ee an a ee be Nias te deta su a aee A Pho bon Poknthy @ yD etRy Ste Mt Hale G9 hese ds ben ky ha te bate lg he rh Wr ae ey Ue et fos Gok c ee AE ed ened © Oe eA Bek Meet nat lhe Qt & ee beihi 1,4 Y Mh lca sibel yah Whig Le Mig OOS h Melt gti hy td Wall HO) ree lity ity REET bets Ope ty ieg & Ng Wee 8 ; wn tae be Bs iy beds thu tt ee ee Poe Wi aaee a Ad bb hae bat 2b de fiber et, Oe 02 TE if ays pee Apis aye: Ue pr at a Aer aC ee Phe baht et het ea hei Thc bol he Cyt Ris eh CE Vee hal oles he. Behl OE gerbe gard baa ‘ tidetida a Be pha ty ot CU eee bt het Oe we eo ae soda ‘ yore Gok Bet Oe ° wuts Dae% Ga teli te tet hott th ate ‘ . " yd? bod ss tg aah Pre ea tat Se ee te Pee ee) oi 44 j a vat & Othe d tee Mebild Walt sa hed # hoa He Oe ed & 6 beh 4-4 te 2% *,° Pye ae ag fea bye ke Wie hee. AA on oe tt beta abe ‘eat , hedcdee Weise bi hg eS steht ie” rae ee OL EL ek tet ehete Botte Hed he © et Aden Ly e-4R Pee Met Sree) te Wat koi eae edd e8 bares Aaa t yt Pot Helis § f Byer tak ‘ 9 6c% thy Pie ee ee wy & 24 80 ES nad for CA aed tr rer a eee Pe ee | hod the Ret a Weed: FB pe TU ee oe ee ee ha Gm, dnt trae Nol bed A elt tse 4 By itd wa hy bee Fe AGG trtebs “ “wea ve ro) og deer Hd ae Oe ak Me LOO Ae Am are ByAn ae waeve + eta are Aa " i erie irc eT Lee ee tak) shed fe eure th cats re gas soe Ge Ae Ra bk: Ste ae eek Wie aw bbiemperd at a Pee ee PRESEN PLAT a eek UP a tae ty Bye Aare tes a. 42 ‘ oa tae CHA AE ee 6A AM Get tioes WE te ee * Pore art Pee rad be Kole ee a TT. 4 RL ta? iin ard + heh Be ty £ Bye) Oy EAU TH ke tA et Eg Utes, de Ge Oo" Te aad Ge k @ Gy led sie tae Pa ea Reise ars LRA he GA Hy Ltn tim Soe fi hehe at Re eee. Paty ie hate = 3 Sy 9-8 es ‘ ; iu Ter mat Pe re fallagh Boob he Howe Foteee Be he Kies Oto Ge 4 “SNe +t Hat tee panes te adel Bt) wii! Wietedaa Tye 501i fe Bee eae Bet) t S97 rh 7¢ Eh Dy th A) em Oe AE thd ett aL St ee et SHE bE se Pack: G 2S) ecg SE Ew, eb Tate. 4.4 heey nese fot Hie MRE ey Hotty deflate ACI eL cet. od “ ‘ or ee me ‘4 9 ‘ Hedge ee oe oa eed ¥ Sea Behe ee o “ « ’ ‘ eed be ‘ wd « yet. Pte at be ga Ge a Gee Clee Aik op es er es Gide Gadd GLE oe 4 © s J ' te, ede Atal . i4 A ee tei ee core Gio tk theo ge re OE AU da te di de thot Ot 4S Ath" 8~ Fits aen ‘ my te Ba ake Holo Dade Qantas Wei Fike che Moar te ge Mee ae Vas -¥ie is fea te) was need : 78 " hee y Aes hy Ok ee Oe ee See Vee edhe EG We liag wee Ce eRe hs mere bee She St wae G4 456-4 Aeuaeagy & 4.4 we oh Ye wets Oe oe ener ck eh coe ah de tore wat CWP BHeGy test sated Wa be tises rade be Fe i Bete Sek ae y 1h 4 @ eae 4 5 ies hed dei het ae Tr Perec UR Se eae as woe got we eo #291 Gee-5. 8 et ain ‘ dtodd i “ 4 ate bd dat ded soem Na te Teeter gna st wed vee ets Lae ho Hid eUraree te ese Sy et Ue Re Gs oe bet 4 8 aed Pi eo ee, ee y HE OA ete AO Meth exh Met eg dat Ga adidas GLE Nw pF Lip Arie Gig peruse Gaiemee Cost da te ert # eb ae GAY, dae ROT Ge Stee 4 ' 1 4-8 1 ia Hee aed aoe} ree re) yi Met og ae Gon heath ag tie tae heey Neate: we bee chs (0h ae Cw Cait ee FF Fela Mae ; Pen rk, 70 WC en EUR Ck COI ate OL Aah Chita bitter hs FOOTE eed Sch Mh RSA. A ahaha , octets (pew Met gee Gate we de 05 18 wh Hid Selb ibe eid: +. ‘de bo 1ere Le ty yan a Be OMl nm ys “o ‘NN = pee PROCKEDINGS AND TRANSACTIONS OR “REE LIVERPOOL BIOLOGICAL SOCIETY. VOL, OCXEE SESSION 1907-1908. LIVERPOOL: C. Tintine & Co., Lrp., PRINTERS, 53, VictoRIA STREET, ESOS. CONTENTS. . I.—-PROCEEDINGS. Office-bearers and Council, 1907-1908 . Report of the Council . Summary of Proceedings at the Meetings List of Members . Treasurer’s Balance Sheet . TI.—TRANSACTIONS. Presidential Address—‘‘ The Seed Production of Pinus sylvestris.’ By W. T. Haypon, F'.L.S. Twenty-first Annual Report of the Liverpool Marine Biological Committee and their Biological Station at Port Erin. By Prof. W. A. Herpman, D.S8ce., F.R.S. Report on the Investigations carried on during 1907, in connection with the Lancashire Sea-Fisheries Laboratory, at the University of Liverpool, and the Sea-Fish Hatchery at Piel, near Barrow. By Prof. W. A. Herpmay, D.8c., F.R.8., AnpREw Scott, A.L.S., and James Jounstone, B.Sc. “Cancer” (L.M.B.C. Memoir No. XVI.) By Josrpx Prarson, M.Sc. “Methods of Plankton Research.” By W. J. Daxtn, M.Se. : : ; : PAGE Vli. Vlll. 1X. Xl. XV111. 30 98 291 500 PROCHKEDINGS OF THE LIVERPOOL BIOLOGICAL SOCIETY. OFFICE-BEARERS AND COUNCIL. Gx- Presidents : 1886—87 Pror. W. MITCHELL BANKS, M.D., F.R.C.S. 1887—88 J. J. DRYSDALE, M.D. 1888—89 Pror. W. A. HERDMAN, D.Sc., F.R.S.E. 1889—90 Pror. W. A. HERDMAN, D.Sc., F.R.S.E. 1890—91 T. J. MOORE, C.M.Z.8. - 1891—92 T. J. MOORE, C.M.Z.S. 1892—93 ALFRED O. WALKER, J.P., F.L.S. 1893—94 JOHN NEWTON, M.R.C.S. 1894—95 Pror. F. GOTCH, M.A., F.R.S. 1895—96 Pror. R. J. HARVEY GIBSON, M.A. 1896-—97 HENRY O. FORBES, LUL.D., F.Z.S. 1897—98 ISAAC C. THOMPSON, F.L.S., F.R.M.S. 1898—99 Pror. C. 8. SHERRINGTON, M.D., F.RB.S. 1899—1900 J. WIGLESWORTH, M.D., F.R.C.P. 1900—1901 Pror. PATERSON, M.D., M.R.C.S. 1901—1902 HENRY C. BEASLEY. 1902—1903 R. CATON, M.D., F.R.C.P. 1903—1904 Rev. T. S. LEA, M.A. 1904—1905 ALFRED LEICESTER. 1905—1906 JOSEPH LOMAS, F.G.S. 1906—1907 Pror. W. A. HERDMAN, D.Sc., F.RB.S. SESSION XXII., 1907-1908. resident ; W. JY) - HAY DON, E.L:S. Bice- Presidents : Pror. W. A. HERDMAN, D.Sc., F.R.S. JOSEPH LOMAS, F.G:S. Hon. Creasurer : Hon, Librarian: W.ds HALLS. JAMES JOHNSTONH, B.Sc. Bon. Secretary: JOSEPH A. CLUBB, M.Sc. Council : HENRY C. BEASLEY. A. LEICESTER. R. CATON, M.D. R. NEWSTEAD, M.8c., F.L.S. M. CUSSANS, B.Sc. (Miss). ~ J ie O CONN HIG, LR. Ce. OULTON HARRISON. JOSEPH PEARSON, D.Sc. W.S. LAVEROCK, M.A., B.Sc. T, C.-RYLEY:. DOUGLAS LAURIE, M.A. L. R. THORNELY (Miss). Vili. LIVERPOOL BIOLOGICAL SOCIETY. REPORT of the COUNCIL. Deurina the Session L90T-1908, there have been seven ordinary meetings and one field meeting of the Society. The latter was held in conjunction with the Manchester University Biological Society, the Liverpool Geological Society and others. By the death of Mr. T. C. Ryley the Society has lost one of its oldest members, and one who, from the year of his election, took an active interest in the affairs of the Society, both as a member of the Council and latterly as the Honorary Treasurer, which position he occupied for a period of ten years. The Council desires to record its appreciation of his services, and of the great loss sustained by his death. The communications made to the Society at the ordinary meetings have been representative of almost all branches of Biology, and the various exhibitions and demonstrations thereon have been of great interest. By invitation of the Council, Prof. R. H. Yapp, M.A., of the University of Wales, Aberystwyth, lectured before the Society, at the May Meeting, on “ The Vegetation of the Fenland.” The Library continues to make satisfactory progress, and additional important exchanges have been arranged. The Treasure1’s statement and balance-sheet are appended. The members at present on the roll are as follows :— Ordinary members - - - - - - 06 Associate members - . - - - - 38 Student members, including Students’ Section - 55 Total ~ Br 114. ~ 4 SUMMARY OF PROCEEDINGS AT MEETINGS. 1. SUMMARY of PROCEEDINGS at the MEETINGS. The first meeting of the twenty-second session was held at the University, on Saturday, October 12th, 1907. The President-elect (W. T. Haydon, F.L.8.) took the chair in the Zoology Theatre. 1. The Report of the Council on the Session 1906-1907 (see ““ Proceedings,” Vol. XXI., p. vill.) was sub- mitted and adopted. 2. The Treasurer's Balance Sheet for the Session 1906- £907 (see “ Proceedings,” Vol. XXI.; p. xx.) was submitted and approved. 3. The following Office-bearers and Council for the ensuing Session were elected :—Vice-Presidents, Prof. Herdman, D.Sc., F.R.S., and Joseph Lomas, PGS. - chon. Treasurer, |W ) J:.5 Hallse "| Hon. Librarian, James Johnstone, B.Sc.; Ilon. Secre- tary; Joseph A. Clubb, M.Sec.; Council, H. C. Beasley, R. Caton, M.D., Oulton Harrison, W. S. Laverock, M.A., B.Sc., R. Newstead, F.L.S., J. H. O’Connell, L.R.C.P., and Joseph Pearson, D.Se. 4. Mr. W. T. Haydon, F.L.S., delivered the Presidential Address gn “The Seed Production of Pinus sylvestris’ (see “Transactions,” p. 1). A vote of thanks was proposed by Mr. R. Newstead, seconded by Mr. T. C. Ryley, and carried with acclamation. xX. LIVERPOOL BIOLOGICAL SOCIETY. The second meeting of the twenty-second session was held at the University, on Friday, November 8th, 1907. The President in the chair. 1. Exhibition by the President of a large seriesiias micro-photographs made in the preparation of the inaugural address on ‘The Seed Production of Pinus sylvestris.” 2. Dr. J.-H. O’Connell gave an-account of the new Colour Photography, and exhibited a series of autochromes. 3.> Mr. "W: D; -Brown” exhibited, -with -remarkeees collection of wind-etched stones. 4. Prof. Herdman submitted the Annual Report on the work of the Liverpool Marine Biology Committee and the Port Trin Biological Station (see Transactions, p.'33). The thard meeting of the twenty-second session was held at the University, on Friday, December 13th, 1907. Jy ) y b) ’ The President in the chair. 1. Dr. H. E. Roaf briefly submitted a preliminary note on the digestive secretions of certain mollusea. 2. Mr. J. Pearson, D.Sc., gave an interesting account of the Biological Station on Ileligoland. The fourth meeting of the twenty-second session was held at the University, on Friday, January 17th, 1908. 1. On the motion of the President, the following Resolution was adopted in silence :— . j SUMMARY OF PROCEEDINGS AT MEETINGS. X “We, the members of the Liverpool Biological Society, wish to express our sorrow at the .death of Mr. 'T. C. Ryley, and our deep sympathy and condolence with Miss Ryley and family in their bereavement. Some of us mourn Mr. Ryley as an intunate friend, and all bear testimony to his hearty kindliness and ever ready helpfulness.” 2. Mr. Oulton Harrison submitted a series of lantern shdes illustrating living lepidoptera, made by - Dr. Hugh Main. 3. Dr. J. O'Connell gave an account and exhibited specimens of living South African amphibians. 4. Mr. J. Johnstone, B.Sc., submitted the Annual Report of the Investigations carried on during 1907, in ‘connection with the Lancashire Sea Fisheries Committee (see “ Transactions,” Dp. a): The fifth meeting of the twenty-second session was held at the University, on Friday, February 14th, 1908. The President in the chair. 1. Mr. H. C. Beasley contributed a note on some recent finds at Storeton, including some good impressions of Equisetites keuperina. The sixth meeting of the twenty-second session was held at the University, on Friday, March 13th, 1908. The President in the chair. © Mr. J. Pearson, W.8c., submitted - the’ LM.B.C: memois on “ Cancer ”’ (see “ Transactions,” p. 291). Xll. LIVERPOOL BLOLOGICAL SOCIETY. The seventh meeting of the twenty-second session was held at the University, on Friday, May 8th, 1908. The Vice-President (Prof. Herdman) in the chair. 1. Prof. R. H. Yapp, M.A., of the University College of Wales, Aberystwyth, gave a lecture on the * Vegetation of the Fenland,” illustrated by a beautiful series of lantern photographs. The eighth meeting of the twenty-second session was the Annual Field Meeting held at Hilbre Island, on Wednesday, May 29th, in conjunction with the Manchester University Biological Society, the Liverpool Geological Society and others. At the short business meeting held after tea, on the motion of the Vice- President (Professor Herdman) from the chair, Prof. Benjamim Moore was unanimously elected President for the ensuing session. ee a. "? ee — . Vv 66 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. towards Niarbyl, No. IV. towards the Calf Island, and No. VY. off Spanish Head (fig. 4). The nets to be compared were:—two vertical deep-water, the Nansen and the Petersen-Hensen, an1 three horizontal, one weighted and the other two surface. In addition a shear-net gathering was taken on occasions from intermediate waters. Hach haul of the horizontal nets was a 15 minutes one. I give here (p. 68) in tabular form, my first state- ment of results, which may require to be modified in detail or supplemented later on, but which may be taken as substantially correct. | Whether one looks at the hauls with the same net at the one locality on different days, or at neighbouring localities on the same day, the want of uniformity both in quantity and in quality is striking. The range for all nets is from 0°5 c.c. to 164 c.c., and the same for the Nansen; for the Petersen-Hensen it is from 0.5 to 64.5 ¢.c., for the weighted open net from 5.5 to 41 e.c., for the surface nets from 1 c.c. to 42°5 e.c., and for the shear-net from 11 to 78°5 ¢.c. The diagram (fig. 9) shows graphically the proportions between these hauls. One or two broad features of the collection are obvious. In the earlier part of the time, up to about the middle of April, Diatoms were abundant, and nearly all the gatherings had a greenish tinge. During that period the plants were more abundant in the bottom waters, and the animals at the surface. Day after day we found that the two closing vertical nets hauled up from 20 to 10 fathoms were of a brownish- green colour and contained (especially the Nansen) an abundant gathering of Diatoms. The surface nets during this time contained more Copepoda. On April 15th and 19th, however, when the change in plankton was taking place the Diatoms are found to be mainly on the surface and the Copepoda below. Ag an example of wide distri- MARINE BIOLOGICAL STATION AT PORT ERIN. 67 bution I may cite April 10th, when the nets gave con- sistent results all the afternoon at three localities north of Port Erin, the Diatoms being in all cases more abundant at the bottom and the Copepoda on the surface. We were fortunate enough on one occasion to obtain incontrovertible evidence of the sharply defined nature of a shoal of organisms, forming an instructive example of how nets hauled under similar circumstances a_ short distance apart may give very different results. On the evening of April Ist, at the ‘‘alongshore ” Station IIT, north of Port Erin, off the ** Cronk” one mile out, I took six simultaneous gatherings in both surface and deeper waters. Two of the nets were the exactly similar surface tow-nets which I have called B and CC. At half-time, as the result of a sudden thought I hauled in B, emptied the contents into a jar, and promptly put the net out again. This half gathering was of very ordinary character, containing a few Copepoda, some Diatoms and some larve, but no Crab Zoéas. At the end of the 15 minutes, when all the nets were hauled on board, all the gatherings, including B, showed an extraordinary number of Crab Zoéas rendering the ends of the nets quite dark in colour. B was practically the same as C although B had only been fishing for seven minutes. It was evident that at about half-time the nets had encountered a remarkable swarm of organisms which had multiplied several times the bulk of the catch and had introduced a new animal in enormous numbers. Had it not been for the chance observation of the contents of B at half-time, it would naturally have been supposed that, as all the nets agreed in their evidence, the catches were fair samples of what the water contained over at least the area traversed—whereas we now know that the Zoéas were confined to at most the latter half of the traverse and may TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 68 FET 9Z cd Da Peace Ne a ee ale | aaa (hahahahaha i ihe 2 ja fee) Nd “dD 91 +¢-86 ‘Nd ‘OD ‘a G& N&O 'a!| T0€ ‘Nd ‘0° 4% sete’ “TTT Fete eee Vv ve) ‘a cI+¢-11 Fe) ‘Vv 70) C.6T avowwa, ' "lL “Seeese (Naw “meee diein UL) | ofulwelere = olan miner . ‘TIL "3249 Ih | Cr ~— O1+¢-9L | val ze) 6 a EE | (i: C.6 ee ed “F "4219 ‘II ‘N ~ ‘al : F1I+8 | aes aia aS Se ONES ie Ree onli rae) mae oii Fat Keg “A ‘en ‘OI a0 OBELGIT® I oer [feessee’ Wp oseeten 7] eaten ep saaie = SP ame “TTT aeag | “OT gd hs 6 Pa G-8th 19) él vo 6 (05 CG 90S ae ‘da GS8It+el | xer SE ‘¢ ¢-8¢ id }->- 4S ee I 348 || “OT Cl. “ty OZ+§1 eaeocthae’ “« *,| Yyeeesee “ile dceverae §».°') “YVepevaa, “i Stee oat Al)” OMad ee) eee ee en ale ‘TIL *4e49 ‘OL NOE Ginter ne Seer Apress oho eee Mag teers SAL” gene ome le ge coe ae | Aeg Tt a 6 OED roi | mena a ak a Os ce heen ee Rc ea act a | [ocac THT 2239 || °6 7 N ‘Da c-11+6 pea G-8 dad OT yat 1 ae | dea ‘IT “#*48 || 6 ie a Gi &ZT8 WW OW Od ¢-O1 ‘d C-GE EGE Of> | ene I ‘3*48 || 6 in Oe -| TLL Vig ego) Gt CT a 6F ‘da OShe ee aes II °¥48 || °8 ‘d | EL +06 al 1G ‘dad | €L ‘da G:0) 2a eee ‘T 248 || °8 9 *: c €I+ZI eigicla wen) | ‘Vall ercicieice ||| 4 me eleqeicne | eccces ‘tf ##eeoeclos i / sececs |licleetee keg aC | al 9 aT '0 ‘AV | EL +6 GY. g.GT zat OOT Xa SG Ls se eae ‘II #®48 || “GS ‘Ou I+F1 da g-S aei FOI || ach G:7Oe 1 lee eee ‘TIT “3°38 || F md i c-é1 Cio Wi ¢-G1 Gl 9G ‘dad Stskeme dl Ss TIT “3748 || “P vd CTI ‘* Gr lilo. eeessegne| fmeniee ‘a epg |leco TT aes || > vn -O'N Gir ae | Rar Cras | asco | Deroy emceso aN |p gpa: Re) oe ecoee | eect: seq “a ‘a || -e fay OU AG 13) CG. a aePall N “Gi iG eeeeee eas cies aii Ge eee eeeee aul 38490 WG ‘Vv zal ia V Xai 9T ecccce | eeecce ‘qd 61 ee eeeseee All "4240 Ti Z, Vv ve) | CZ+8 NO “dt ST eeeeee | erewinis) [ile wie weteisor |] afarnieeje) alll starclalefelerele ‘III "4249 i ady ot O-d 6+8 ece Siaieatis BR ae |e raster ||| Retna) EE dace. Fi ||[Soccceace “AT 2239 || “6% “421 “SUISTURSIO, ae) “STUSTUR SIC) vO ‘STUSTURSIQ) © ‘o'Q | “stusTURSIO a” sord) eS) SAO) pe@) | “ALVIVOO'T aLVd oo = ke one eee ee | ee ‘SLOAN GOVEUAG OMY, “LON-LHOIA "NASNVN "NUSNG A -NASUALG | ‘aneys staddg snuepeg ‘Og ‘ vanetdoyi9 ‘C) ‘spodvoog earey vy ‘topdnen NY fesnpeyT “yy ‘s88o ys ‘oy ‘stozeiq “q+ terdneyy podedog ‘Ng ‘epodedog -9 ‘tepdney snueeg “Ng ‘espy “vy ‘(pazjtuto you-reeqg) LO6T Josey ‘NIU LUO FO pooyANogystotl oY} ULSNOILVLG oAYy Ye SLAN OAY OY} FO SLTIASAY TVAANAL) 69 2 FO AO Fy VAS ONS SO) aaee SACAAAS Oo OOO ‘BARE ;Add.Sd0 Zine ee AT PORT ERIN. OO KOO AA ee] Te STATION MARINE BIOLOGICAL 9 | o00000 > cpodec | 6odobe | ee eeee eenaedy Sa. | reiererere Aeg “a ‘qd "1% Cle el (OG ¢-01 0 'a Gl IO) GL Tie |lenen "A 2839 |] “LZ GL+G-1L+¢-§ O20) Gd OL a Gas re 2a Ch mes "A ‘#48 || “LZ gt+9 | 0'a G11 0'd € Ov COC eas "A “4848 || cL 2 Ih NO ‘0 8 "NO c.0 "NO CO Ras _ A "3898 |] 9% ae (iris wget Re ices ne RIE Ms Semis lien vorea alleen oll” Achy |e Reqece fe leoe Oi Os |e Ore) Gal ae NO cds) Fk? Oe NOG Ge ee "T3899 || 98 Oeeaict etek |e eer a Were ce ne oe) ieeeeces levee hog Hoa | sez on oO ect? P| cereal Myreccne s Ne adeem kes see BG e dee meal eat ees TIT 3@98" || “Ge Coit Sie | OP NIG) C6 ‘NO OG "NO lee | ieee "A 2849 |] "SS G7 ee Ala aes eel bee eae Ne a ems lee eenee “AT mag || ‘eg GP+G.g ‘da 0 "NO 06 | "ad ‘0 °NO Z ‘0 “NO SL eS ee “IIL “3839 || “$3 OI+8 | efeteterece. 0 OM ereyerecevequemlil) lomAbre araielereme 9 Hl ul evavuorete | Peete ai) pina eer AV aC E “ay VG Cte et eNO | SLT 0d gg fo can GS TE aeage ll 6G Gel: OG. ailee Gh enn Nag) 91 eH aD c WG OS) SO. Pe ie SER arc G.OIT+€T | Sgoleior eee | RS il! Gv eeieisVers: Full @.e. “erereisreie OM tN caiewlevele Tecilta duelevecicrsin ) will memrelecty. © Ul licrcperees Aeg Td "0% G.9+@.8 | COO COO Se COCOONS ON cocoa s HN Veo ogcoaa sail Peas 13,000 0 Calanus helgolandicus 100 6 Pseudocalanus elongatus ... 850 500 Temora longicornis 2,470 4,750 Oithona similis 100 50 Acartia clausi 250 200 Centropages hamatus 0 200 Coscinodiscus concinnus 8,000 14,000 Biddulphia mobilensis 40,000 70,000 Rhizosolenia semispina 1,000 3,000 Lauderia borealis zn 1,000 0 Thalassiosira nordeuskioldu 2,000 7,000 bs subtilis ... 6,000 0 Cheetoceros teres 0 1,000 Peridinium sp. 500 W) Plutei 500 1,000 Oikopleura sp. 2,000 150 Medusoids oe 50 25 Sagitta bipunctata ... 0 48 Crab Zoéas ... 0 10 This shows very clearly that the two gatherings, although alike in quantity, were unlike in quality. As a sample of the manner in which, as the result of Mr. Scott’s work, we are now recording these plankton hauls, I give here the following table dealing with one of the off-shore stations on a forenoon run in_ the “ Ladybird.” The shear-net haul was taken on the way in, half-way between the Calf Island and Port Erin. 72 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. INe@t Sed! (ic sak. ease aeen Depth in fathoms Catch in c.cm. Biddulphia mobiliensis ..... Chetoceros contortum ..... oe Gaebler. Sie .es: ie decipiens........: - Sociale yy. t ne Coscinodiscus concinnus..... Ditylium brightwellii ........ Eucampia zodiacus Lauderia-borealis ........... Bhizosolenia shrubsolei Thalassiosira gravida ..... a nordenskioldii Rhizosolenia stolterfohti Leptocylindricus danicus ... Ceratium! tured ssscscs-5 cee He PUSUG# Amretecameeccs 58 UPIPOS Giicsisstalpetises (Pe rican my one eee eee Medusoid gonophores_..... Plutei of Echinoderms ..... Sagitta bipunctata ........... Autolytus prolifer ........... Larval Polycheta- ........... Mitraria 7 Sesser enna. Crab zoea Mysis stage of Crangon First stage Nephrops ........ Podon intermedium ........ Evadne nordmanni........... Calanus helgolandicus ..... Pseudocalanus elongatus .. Temora longicornis Centropages hamatus ..... Anomalocera pattersoni Acartia clausi Ror mee Oithonarsimilis.s.... ee seece Copepod nauplii ......)...:.< - Juv. Barnacle nauplii 3. 1 CYPLIS*sage sae: Oikopleuraisp.os..0.0s:-eca Fish eggs, Rockling Common Dragonct........ opkiot 5 (525. ost neeceees eee BUD. japan don ut cemOaacneeeee Whiting Cod) Fxctur: Gy See eee Sprat Spotted dragonet Young fishes, Gadoid ee | Clupecids -i2.2:.. Cee ere ses eee er secree eee see eoeses ee eee eee eee nee ee cer ees eee eee eee eee Ce eeseeereseseereseeres 250 2,000 Pll ll oH etorSe 100 600 150 200 100 400 2,400 300 4,500 3,000 25 bo ? -~J = S| we OS Hensen. Nansen. 500 36,000 2,500 1,500 200 500 1,000 5,000 2,000 500 65,000 1,000 4,000 1,000 Weight. Shear. 250 2,500 1,000 63,000 500 250 2,000 —_ — 4,000 — — 2,000 250 1,000 200 14,000 -- 500 2,000 500 — 1,000 — 134,000 8,500 500 2,000 — 3,000 250 —- 500 -— — 500 1,500 — — 1,000 — 6,000 750 — 100 50 — 120 300 —-:1,800 6 27 123 at =e 1 20 20 250 = 500 ues : oe 8 16 t 10 37 72 “ 4 4 ll - = 150 50 : 120 1,200 850 i 770. 1,600 500 4 150 2,300 750 + ss er 50 " 125 1,600 50 50 150 a — 7.000 250 —— Corn MARINE BIOLOGICAL STATION AT PORT ERIN. 73 During the recent summer vacation (August 9th to September 20th, 1907) with the assistance of Mr. Buchanan-Wollaston and others, I again worked the plankton nets on every possible opportunity from the s.y. “Ladybird,” trying to make a still more intensive study of a limited district. On this occasion over 300 gatherings were taken in 30 days, an average of 10 per day. On one trip (September 20th) 36 gatherings were taken in an afternoon, 1n a small area of only about two miles extent, as follows :— Locatiry A :—6 miles out, W.N.W. of Bradda, over 30 fms. 1. Hensen and Nansen nets let down to 30 fms. and hauled up 10 fms. (30-20). ae 55 = 5c 20 fms. a 35 LO fms, (20-10): 2 = as B 10 fms. ‘5 » 10fms. (10-0). : {open to 4, ” ” ” 30 fms. 99 ” ( ee (30-0) Weighted open net (A) and two surface nets (Al and A2) along with shear net (Sh. 1) at 15-20 fms. Weighted open net (B) and two surface nets (Bl and B2) along with shear net (Sh. 2) at. 7-8 fms. (These each j-hour hauls; the one set taken immediately after the other.) Mill water bottle at 20 fms., strained at the time. o » oat 20 fms., strained on shore. Locatity B:—8 miles out W.N.W. of Bradda, over 30 fms. 1. Hensen and Nansen nets let down to 30 fms. and hauled up 10 fms. (30-20). 2. ” ” 2 20 fms. > 29 10 fms. (20-10). 3. ” ” ” 10 fms. oe) oy) 10 fms. (10-0) 4. Nansen (alone) : 53 30 fms. fs », to surface (30-0). Weighted open net (C) and 2 surface nets (Cl and C 2) along with shear net (B1) at 7-8 fms. Weighted open net (D) and 2 surface nets (D1 and D2) along with shear net (B2) at 15-20 fms. (These each j{-hour hauls; the one set taken immediately after the other.) Mill water bottle at 20 fms., at 10 fms., and at 5 fms. The object I had in view on most occasions was to sample the various layers of water, as well as to compare neighbouring localities and adjoining dates, and the following diagrammatic statement of certain of the hauls taken on September 12th will illustrate the plan of work adopted to differentiate the zones : — 74 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Surface Sh.2. Fic. 10.—Diagram to show the hauls taken at one station. I.—VI. represent hauls of the vertical closing nets; W.n. (weight net), Sh. 1 and Sh. 2 (shear net) and the two surface nets represent horizontal or oblique hauls. The numbers 5 to 60 indicate depths in fathoms. Here, out in the middle of the Channel between Ireland and the Isle of Man, the depth was about 65 fathoms, and we sank our vertical nets down to 60, and hauled them up through the lower 10 fathoms (L.), the lower 30 (II.), and the entire depth (III.), then through the zones 30 to 20 (IV.), 20 to 10, and 10 to 5. | MARINE BIOLOGICAL STATION AT PORT ERIN. 75 That brought us in touch with the surface zone through which the weight-net, the shear-nets, and the surface-nets had ranged. In this way we hope to be able to localise the constituents of the fauna obtained in a vertical haul such as III. The full details of the results obtained from these 300 hauls taken in summer, as well as of the 276 taken at Easter and the 80 of the previous summer, will be given in a paper by Mr. Scott and myself, which we hope to have ready for the Annual Report of the Lancashire Sea-Fisheries Laboratory early in 1908; but in the meantime it may be of interest to readers if I give here one more list showing the results of a haul on Station Y. inside the Wart bank (see fig. 4). One remarkable feature of this occasion was that the Hensen net hauled up from 14 fathoms contained 150 specimens of what is considered by Mr. Scott to be a new species of Leptopsyllus, while the Nansen net used at the same time, and at the same depth, on the other side of the ship, caught twice as much material but not a single specimen of the new Copepod. The surface nets (I. and IT.) are also somewhat divergent in their results. . Fe ee ie Te Hen. Nan. Weight. Depth in fathoms ............... 0 0 — = = DEMME COTA occ ciciess oovcees 4.5 3 3 7 30 Biddulphia mobiliensis ...... 700 750 20 50 1,000 Chetoceros contortum ...... — — 15 10 — i GeCIpIENS) |e... hsc0 — — 15 — —_ Coscinodiscus radiatus ...... — — 10 _ — ss concinnus....... — 200 —_ —_ _— Rhizosolenia semispina ...... 250 1,000 25 10 _— MEMEONONINY TUSUS .......--00cecocsee = 500 10 10 500 es PLUS iiss. Sees nace 250 2,750 70 20 1,000 oT 250 300 5 — — Trochiscia brachiolata ......... a= 200 10 25 250 Sagitta bipunctata ............ 21 21 — ] 125 Tomopteris onisciformis ...... — 1 — = as Larval Polycheta ............ 200 — 40 a = LS 6 ec 75 — — —- — MEMZIOD, oni ccncteacesvoeectrers — — — _ 2 Be AMOLBIOPS 5.0. .0her0crye p00 1 76 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Mysis stage of Crangon ...... 5 3 _ 3 36 Podon intermedium ............ 10 — a any 15 Calanus helgolandicus ......... 34 7 — — 67 Pseudocalanus elongatus 4,500 830 100 325 23,000 Temora longicormis~.....:...... 200 25 8 10 700 Centropages hamatus ......... 150 25 5 10 200 ACArtiasClAUGNe ales eta’ eilee se aipivielele 1,255 150 8 100 6,000 OithonmaLsuMmMiliSaeesccle ect ose. 4,500 35200 35 15 6,500 Paracalanus parvus .........06 200 150 4 6° 2 SS TsiasiGlavape sicher. sccje-e-e ven — 25 — — 300 Leptopsyllus sp. ....... 030... — -— 150 — a Ameira intermedia ”./).....6.. 7. -— — d = = ZVAS SOOASIT | issecceseeaeserse — — — ss ps Copepod nauplii ............+... 17,000 22;500 340 2,450 = 38,000 mi SVU Woe accel cients de 15,000 750 40) 600 19,000 Gasteropods, larval ............ 250 200 20 50 500 Lamellibranchs, larval ...... 250 509 20 50 500 Orkoplewura sw eeeaeceenins «eter 875 900 25 tO — ASCIGIRM EGER. Lots dante slareraalaetar 1,500 1,500 a= — 2,000 NOUME TSMES Serine cmecu cesses — — — — 6 COMPARISON oF THREE FisHiInG BANKS. In the “ Annals and Magazine” for 1839 Professor Edward Forbes published a short paper entitled, ‘‘On a shell-bank in the Irish Sea, considered Zoologically and Geologically ’ (Ann. and Mag. Nat. Hist., Vol. TV., 1840, p. 217), in which he recorded the results obtained during some years of occasional dredging on a scallop bank lying opposite Ballaugh off the North-West of the Isle of Man. As these observations extended over seven years previous to 1839, if we reckon from a period about the middle of his work we may consider that we are now dealing with a ‘record of the condition of the marine fauna on this bank well over 70 years ago. It seemed to me that we had here an opportunity, such as rarely occurs, of determining whether any change had taken place in a limited, well- defined area after a considerable interval of time. Forbes, unfortunately, did not deal with all groups of animals, and in fact he paid most attention to Mollusca, and only recorded in addition the Echinodermata and a few of the — Nii i MARINE BIOLOGICAL STATION AT PORT ERIN. “1 "| 1SLEoFMAN ~~ Prgtish Mize Seytad X er > * Sudo Fy Tm Sa RAD pacity mae ere y Fig. 11.—Map of the Isle of Man. Ballaugh lies a little inland half-way between Kirkmichael and Jurby Head. Zoophytes. Still we may be thankful for what he has given us at such an early date, and it will be interesting to see what can be made of it in comparison with our 78 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. observations at the present time. He ends his paper with the following paragraph :— ‘T have drawn up these observations chiefly in the hope of inducing others to present us with similar reviews of the shell-banks of our coast. Geology and zoology will gain as much by inquiring how our marine animals are associated together as by investigating genera and species, though the former subject has, as yet, been but little attended to in comparison with the latter.” That sentiment is in thorough accord with the views of nature expressed in these L.M.B.C. reports, and it is in the same spirit that we now examine, and hope to add to Forbes’ observations of seventy years ago; we are only continuing, and I hope extending, the work that he began so well. As yet we have had only a few days’ work on the Ballaugh bank, and if we have already found more species than Forbes records, that does not necessarily lead us to the conclusion that the fauna is now more abundant, since we have dealt with some groups of animals that were not given in the older list, and possibly our modern methods with a convenient steamer, an Agassiz-trawl and wire-rope enable us to work more rapidly and effectively. But look- ing merely at the groups recorded by Forbes we find that we have not found quite so many Mollusca, but a great many more Zoophytes and Polyzoa. The bank seems to be particularly rich in Nudibranchiata and in Ceelenterata ; in one haul we counted 200 beautiful colonies of Aleyonaum digitatum, including both white and orange forms. There is no object in making a detailed comparison or attempting to draw any conclusions until we have done more work on the bank, and accumulated a greater number of records. It occurred to me, however, that it would be interesting to extend the range of the observations by MARINE BIOLOGICAL STATION AT PORT ERIN. 79 including two other shell-banks under shghtly different conditions, and showing apparently very different bottom- deposits. These are (1) the Train bank, lying about 8 miles N.W. of Port Erin, where there is a good deal of mud mixed with the sand; and (2) the Wart bank, lying 2 miles S. of Spanish Head, near Port St. Mary, and having the bottom formed chiefly of broken shells and other calcareous Rtvsoneceacoonoetcinnnenimnnniannee INNO LS SIOMMNIO INTIS v0 ‘ Fic. 12.—Showing the Agassiz-trawl being swung in on the derrick. fragments. These three banks—the Ballaugh, the Train, and the Wart—lying in the “Coralline” zone off the Isle of Man, ought, in the end, to give us interesting information in regard to the common characteristics and the individual features of such fishing banks in our seas. G 80 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The work will be gone on with whenever opportunity offers, and we shall hope to return to the subject in a future report. L.M.B.C. Mermorrs. During this year two important Memoirs have been added to our published series, and two additional ones of still larger size are now nearly completed. No. XLV. on Licts, the large shore Isopod Crustacean, by Mr. C. Gordon Hewitt was issued in January, and Mr. Chadwick’s Memoir on ANTEDON, the rx ~~ Fic. 13.—Antedon bifida, the rosy feather-star : 1. Adult, nat. size; 2. stalked larva, nat. size; 3. larva magnified. Rosy-Feather-Star (fig. 13), illustrated by seven beautiful plates, appeared in June. Mr. Dakin’s PEcTEn, the Scallop, is now in my hands and will probably be out in December or January; and Mr. Pearson’s CANcER (the edible crab) will follow soon after as our seventeenth } £. MARINE BIOLOGICAL STATION AT PORT ERIN. 81 Memoir. Still others are in active preparation. We frequently receive, from heads of laboratories, suggestions of types that it would be useful to get undertaken, and, from naturalists, of Memoirs that they are willing to write. As I remarked last year this unusual amount of excellent material which the Committee is happy to be able to issue to the scientific world, is, however, embarrassing from the point of view of expense. Lithographic plates, such as these memoirs require, seem to become more costly, and with the growing elaboration of the subject more detailed illustration is necessary. The Committee are therefore very grateful to those friends who have kindly by special donations enabled the Treasurer to meet the expenses of plates for several of the above- mentioned Memoirs. Further donations towards the illustrations of those still unpublished will be very welcome. The following shows a list of the Memoirs already published or arranged for :— Memoir I. Ascrpta, W. A. Herdman, 60 pp., 5 Pls., 2s. a II. Carpium, J. Johnstone, 92 pp., 7 Pls., 2s. 6d. 5, III. Ecurnus, H. C. Chadwick, 36 pp., 5 Pls., 2s. _ IV. Copium, R. J. H. Gibson and Helen Auld, 26 pp., 3 Pls., 1s 6d. - V. Aucyonium, S. J. Hickson, 30 pp., 3 Pls., 1s. 6d. 7 VI. LErPEoPHTHEIRUS AND LeERN@=A, Andrew Scott, 62 pp., 5 Pls., 2s. » VII. Linevs, R.C. Punnett, 40 pp., 4 Pls., 2s. » VIII. Pratce, F. J. Cole and J. Johnstone, 260 pp., Il'Pls. 2 78: | — IX. CHonprvus, O. V: Darbishire, 50 pp., 7. Pls., 2s. 6d. eX. Patetia, J. R.A. Davisiand. H. J. Fleure, 84 pp., 4 Pls., 2s. 6d. 82 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Memoir XI, Arenicota, J. H. Ashworth, 126 pp., 8 Pls., 4s. 6d. », NII. Gammarus, M. Cussans, 55 pp., 4 Pls., 2s. ,, XIII. Anurtpa, A. D. Imms, 107 pp., 8 Pls.; 4s. 6d. » ADV. Livia, C. G. Hewitt, 45 pp. 4 Plame » . XV. Antenpon, H.-C: Chadwick, 50° paaeiemeee Xs. Gd. Prcten, W., J. Dakin. Cancer, J. Pearson. . Doris, Sir Charles Eliot. | Oyster, W. A. Herdman and J. T. Jenkins. | Cucumaria, BH. Hindle. | OsTRAcoD (CYTHERE), Andrew Scott. Buccinum; W. B. Randles. | ‘ Buaeura, Laura R. Thornely. ZostERA, R. J. Harvey Gibson. HimantHaria, F. J. Lewis. Fucus, J. B. Farmer. BorrytioipEs, W. A. Herdman. © Curtite-Fiss (ELeponr), W. E. Hoyle. Actinia, J. A. Clubb. TlarticHonpria and Sycon, A. Dendy. Hyprorip, EK. T. Browne. Prripintan, C. A. Kofoid. In addition to these, other Memoirs will be arranged for, on suitable types, such as Pagurus, Sagita, Pontobdella, a Cestode and a Pycnogonid. We append to this Report :—~ (A) The usual Statement as to the constitution of the L..M_B.C., and the Laboratory Regulations ; (B) The Hon. Treasurer’s Report, List of Subscribers, and Balance Sheet. | a MARINE BIOLOGICAL STATION AT PORT ERIN. 83 APPENDIX A. THE LIVERPOOL MARINE BIOLOGY COMMITTEE (1907). His Excettency tHE Ricut Hon. Lorp Racuan, Lieut.- Governor of the Isle of Man. Mer. R. D. Darsisuire, B.A., F.G.S., Manchester. Pror. R. J. Harvey Gipson, M.A., F.L.S., Liverpool. Mer. W. J. Harts, Liverpool. Pror. W. A. Herpman, D.Sc., F.R.S., P.L.8., Liverpool, Chairman of the L.M.B.C., and Hon. Director of the Biological Station. Dr. W. E. Hoye, M.A., University, Manchester. Mr. P. M. C. Kermope, Ramsey, Isle of Man. Mr. A. Leicester, Liverpool. Siz Cuaryes Perris, Liverpool. Mr. EH. Tuompson, Liverpool, Hon. Treasurer. Mr. A. O. Warner, F.L.S., J.P., formerly of Chester. Mr. Arnoxup T’. Watson, F.L.S., Sheffield. Curator of the Station—Mr. H. C. Cuapwick. Assistant—Mr. T. N. CREGEEN. CONSTITUTION OF THE L.M.B.C. (Established March, 1885.) I.—The Ossxcr of the L.M.B.C. is to investigate the Marine Fauna and Flora (and any related subjects such as submarine geology and the physical condition of the water) of Liverpool Bay and the neighbouring parts of the Irish Sea and, if practicable, to establish and maintain a Biological Station on some convenient part of the coast. 84. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. I1—The Commrirrrx shall consist of not more than 12 and not less than 10 members, of whom 8 shall form a quorum; and a meeting shall be called at least once a year for the purpose of arranging the Annual Report, passing the Treasurer’s accounts, and transacting any other necessary business. Iil—During the year the Arrarrs of the Committee shall be conducted by an Hon. Director, who shall be Chairman of the Committee, and an Hon. TREAsuRER, both of whom shall be appointed at the Annual Meeting, and shall be eligible for re-election. IV.—Any Vacancrzrs on the Committee, caused by death or resignation, shall be filled by the election at the Annual Meeting, of those who, by their work on the Marine Biology of the district, or by their sympathy with science, seem best fitted to help in advancing the work of the Committee. V.—The Expensss of the investigations, of the publi- cation of results, and of the maintenance of the Biological Station shall be defrayed by the Committee, who, for this purpose, shall ask for subscriptions or donations from the public, and for grants from scientific funds. | VI.—The Brotoeican Station shall be used primarily for the Exploring work of the Committee, and the Sprctmens collected shall, so far as is necessary, be placed in the first instance at the disposal of the members of the Committee and other specialists who are reporting upon groups of organisms; work places in the Biological Station may, however, be rented by the week, month, or year to students and others, and duplicate specimens which, in the opinion of the Committee, can be spared may be sold to museums and laboratories. i] Rs ety : / es eee. oF ey ae Be Pmt MARINE BIOLOGICAL STATION AT PORT ERIN. 85 LIVERPOOL MARINE BIOLOGICAL STATION AT PORT ERIN. LABORATORY REGULATIONS. I.—This Biological Station is under the control of the Liverpool Marine Biological Committee, the executive of which consists of the Hon. Director (Prof. Herdman, F.R.S.) and the Hon. Treasurer (Mr. E. Thompson). IJ.—In the absence of the Director, and of all other members of the Committee, the Station is under the temporary control of the Resident Curator (Mr. H. C. Chadwick), who will keep the keys, and will decide, in the event of any difficulty, which places are to be occupied by workers, and how the tanks, boats, collecting apparatus, &c., are to be employed. Iii.—The Resident Curator will be ready at all reasonable hours and within reasonable limits to give assistance to workers at the Station, and to do his best to supply them with material for their investigations. ITV.—Visitors will be admitted, on payment of a small specified charge, at fixed hours, to see the Aquarium and Museum adjoining the Station. Occasional public lectures are given in the Institution by members of the Committee. V.—Those who are entitled to work in the Station, when there is room, and after formal application to the Director, are:—(1) Annual Subscribers of one guinea or upwards to the funds (each guinea subscribed entitling to the use of a work place for three weeks), and (2) others who are not annual subscribers, but who pay the Treasurer 10s. per week for the accommodation and privileges. 86 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Institutions, such as Universities and Museums, may become subscribers in order that a work place may be at the disposal of their students or staff for a certain period annually ; a subscription of two guineas will secure a work place for six weeks in the year, a subscription of five guineas for four months, and a subscription of £10 for the whole year. VI.—Kach worker is entitled to a work place opposite a window in the Laboratory, and may make use of the microscopes and other apparatus, and of the boats, dredges, tow-nets, &., so far as is compatible with the claims of other workers, and with the routine work of the Station. | VII.—Fach worker will be allowed to use one pint of methylated spirit per week free. Any further amount required must be paid for. All dishes, jars, bottles, tubes, and other glass may be used freely, but must not be taken away from the Laboratory. Workers desirous of making, preserving, or taking away collections of marine animals and plants, can make special arrangements with the Director or Treasurer in regard to bottles and preservatives. Although workers in the Station are free to make their own collections at Port Erin, it must be clearly understood that (as in other Biological Stations) no specimens must be taken for such purposes from the Laboratory stock, nor from the Aquarium tanks, nor from the steam-boat dredging expeditions, as these specimens are the property of the Committee. The specimens in the Laboratory stock are preserved for sale, the animals in the tanks are for the instruction of visitors to the Aquarium, and ag all the expenses of steam-boat dredging expeditions are defrayed by the Committee, the specimens obtained on these occasions must be retained by the Committee (a) for the use of the specialists working at. MARINE BIOLOGICAL STATION AT PORT ERIN. 87 the Fauna of Liverpool Bay, (6) to replenish the tanks, and (¢) to add to the stock of duplicate animals for sale from the Laboratory. VIII.—FEach worker at the Station is expected to lay a paper on some of his results—-or at least a short report -upon his work—before the Biological Society of Liverpool during the current or the following session. IX.—AIl subscriptions, payments, and other com- munications relating to finance, should be sent to the Hon. Treasurer. Applications for permission to work at the Station, or for specimens, or any communications in regard to the scientific work should be made to Professor Herdman, F.R.S., University, Liverpool. Hensen’s Plankton Net. 88 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. APPENDIX B. HON. TREASURER’S STATEMENT. The list of Subscribers and Balance Sheet for 1907 is herewith appended. The latter shows a small balance due to the Treasurer, which indicates the necessity there is for additional support, as expenses during the past few years have necessarily increased now that the work of the Port Erin Biological Station has been so materially enlarged. The L.M.B.C. Memoirs have proved of the greatest service, both to the senior students in University Laboratories and to investigators in Biological Stations. They have been much appreciated by scientific men, both in this country and America, and are very favourably reviewed in Vature and other papers. These Memoirs are illustrated by lithographic plates, and are necessarily expensive to produce, and, as they are sold at a very low price, the receipts as yet do not cover the cost of production. During the past year, Memoirs No. XIV., “ Ligia ” (a Shore’ Crustacean), and No. XV., “ Antedon™ "(the Rosy-Feather-Star), were published, and the MSS. for several more are in preparation, two, in fact, being already completed and ready to print. Welcome donations of £30 from Mrs. Holt and Miss Holt, and £20 from Mr. 'T. Sutton Timmis, have just been received towards the plates of the forthcoming Memoirs on ‘‘ Pecten”’ (the scallop), and “ Cancer” (the edible crab). Further Memoirs will be published as funds permit, and the Treasurer will gladly receive donations for this purpose, or for the necessary working expenses of the Biological Station at Port Erin. Epwin THOMPSON, Hon. Treasurer. 1, Croxteth Grove, Liverpool, December, 1907. MARINE BIOLOGICAL STATION AT PORT ERIN. SUBSCRIBERS. Beaumont, W..I., Citadel Hill, ee Bickersteth, Dr., 2, Rodney-street.. Briscoe, F. W., Colby, Isle of Man Brown, Prof. J: Campbell, University, os Browne, Edward T., B.A., 141, Uxbridge- road, Shepherd’ S Bush, London Boyce, Sir Rubert, F.R.S., University, Teneo! Brunner, Mond & Co., Northwich.. I Brunner, Sir J. T., Bart., M.P. ee annok Brunner, J. F. L., NP. London ... 2 Caton, Dr., 78, Rodney-street, Liverpool ... Clubb, J. A., Public Museums, Liverpool... Cowley, R. C., Laurel Bank, Garston trellin, John C.; J.P., Andreas, Il. of Man... Crosfield, Harold G., Fulwood-park, Liverpool ... Dale, Vice-Chancellor, University, Liverpool Davis, Prof. Ainsworth, see as pouree: Aberystwyth Dixon-Nutiall; -F. R., J.P., E. R. M. s. oe Elot, Sir Charles, Tere Sheffield .. Gair, H. W., Smithdown-road, Wavertree Gaskell, Holbrook, J:P., Woolton Wood... Gossage, the late F. H., Camp Hill, Woolton Halls, W. J., 85, Lord-street, Liverpool ... Headley, F. W., Haileybury College, Hertford ... Herdman, Prof., F.R.S., University, Liverpool ... Hewitt, David B., J.P., Northwich ee es Hickson, Prof., F.R.S., University, Manchester ... Holland, Walter, Carnatic Hall, Mossley Hill Holt, Alfred, Crofton, Aigburth Holt, Alfred, Junr., Crofton, Aigburth Forward rm re pO FH tt KBPrROoOoODOOrFrRNa Fe HH RB peonprFrRNOrF FE & EDF Pb £44 (2) me Re bp eH CONN FR N FPF OF NY FY WY HF 4 89 S 2S. ey =] Te-er e) Gra oe a a] & QS ye) ee) ene oor ea Sea) lop) 90 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Forward ... Holt, Mrs., Sudley, Mossley Hill ... Holt, P. H., Croxteth-gate, Sefton-park ... Holt, R. D., 54, Ullet-road, Liverpool Hoyle, Dr. W. E., Museum, Owens College Isle of Man Natural History Society Jarmay, Gustav, Hartford, Cheshire Jones, Charles W., J.P., Allerton Beeches Lea, Rev. T. Simcox - Leicester, Alfred, 30, Brunswick-street, bivateael Lewis, Dr. W. B., W. Riding Asylum, Wakefield... Manchester Microscopical Society... Meade-King, R. R., 4, Oldhall-street Monks, F’. W., Warrington... Muspratt, EH. K., Seaforth Hall = Narramore, W., Cambridge Avenue, Gt. Crosby... O'Connell Diels Dunloe, Heathfield-road, Liverpool ce OkelLUR BAL Keias., atten eee. L of tia Petrie, Sir bares, Devonshire-road Pilkington, J. A., Bank House, Maghull ... Quayle, Alfred, 7, Scarisbrick New-road, Southport Rae, Edward, Courthill, Birkenhead Rathbone, Mrs. Theo., Backwood, Neston... Rathbone, Miss May, Northumberland-street, London Rathbone, Mrs., Green Beat tone Roberts, Mrs. Isaac, Thomery, 8. et M., eae Robinson, Miss M. H., Holmfield, Aig hate Ly me Simpson, J. Hope, Ivy lodge, Aigburth Smith, A. T., 43, Castle-street f a Sorby, Dr. H. C., F.R.S., Broomtield, Sheflield a Forward SS. sae 44 1 6 2+ Oe 1 deat 2) arg Leg LS ee jae hh lL Gee Ite ] of oa | Osa fas ee 0 105g 2.270 5 O20 bie ae a a ee a a oe (Sp (Sy Sl Lay Sea aken) Bee OF fF pp LE Saeco Oro: MARINE BIOLOGICAL STATION AT PORT ERIN. 91 Forward... Tate, Sir W. H., Woolton, Liverpool Thompson & Capper, 4, Lord-street, Liverpool ... Thornely, Miss, Nunclose, Grassendale ... Thornely, Miss L. R., Nunclose, Grassendale Timmis, T. Sutton, Cleveley, Allerton Toll, J. M,, 49, Newsham-drive, Liverpool Walker, Alfred O., Uleombe Place, Maidstone Walker, Horace, South Lodge, Princes-park ... Watson, A. T., Tapton-crescent, Sheffield... Whitley, E., Clovelly, Sefton-park, Liverpool Weiss, Prof. F. E., Owens College, Manchester ... Wiglesworth, Dr., Rainhill... ns : Wragg, Sir W., D.C.L., Port St. Mary, Isle of Man Wright, C. H., 9, Cook-street, Liverpool ... SUBSCRIPTIONS FOR THE Hire oF ‘‘ WorK-TABLES.”’ Victoria University, Manchester ... University, Liverpool University, Birmingham 2 eed: Sil D220 iwc 20) O 10736 22 O 2 EO fake © So 0 Pe 1-0 I ft .6 2. 2 0 L 2440 ae et fsck © ihe HO £101 16 O eee iad, £10 0 O 10-0.-0 10050 £30 0 0 The Naturalist’s Dredge. “squvjunoooy pereJsVgy ‘SHHLVAT ¥ “SOOO “7904409 PUNOJ PUY pajy_pNP be ——_____.__ J 0 9, $95 | “LOGI ‘YI0G Laquacsag? ‘1OOdaMAFT a , 2 hs. b . 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Drawn up by Professor W. A. Herpman, F.R.S., Honorary Director of the Scientific Work; assisted by Mr. Anprew Scort, A.L.S., Resident Fisheries Assistant at Piel; and Mr. James JonnstoneE, B.Sc., Fisheries Assistant at the Liverpool Laboratory. (With plates and text figures.) CONTENTS. PAGE 1. Introduction (W. A. H.) - - - - - - 93 2. Sea Fish Hatching at Piel (A. 8. ee - - - - 98 _ 3. Classes, Visitors, &c., at Piel (A. 8.) - - - 101 4. Report on Hensen Net Observations (ARS) = - - 105 5. Marked Fish Experiments (J.J.) - = = - 114 6. Parasites of Fishes (J. J.) - - - - 136 7. Hydrographic Geta (Dex Tey Bassett) - - - 146 8. Blackpool Closed Ground Drawn Statistics ues J. Buchanan- Wollaston) - 172 9. Mersey Shrimp Trawling Satistics (A, J. fenenacene Wollaston) - 179 10. Intensive Study of the Plankton mal the South aud of the Isle of Man (W. A. H. and A. §.) - - 186 11. Memoir on Cancer (the Edible Crab) (J. Pearson) - - 291 INTRODUCTION AND GENERAL ACCOUNT OF THE WORK. On account of my mission to the Ceylon pearl banks in February and March, this Report does not appear this year until a few weeks later than the usual date. There are, however, advantages in the slight delay, since it has enabled one or two of the sections to be more thoroughly worked up. Moreover, as this report deals with the completed work up to the end of 1907, it really, in going to press in April, is appearing in very good time compared with the usual practice of most Annual Reports, 4 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Work Av PIEL. There is comparatively little that need be said about the work at the Piel laboratory and hatchery. Mr. Scott’s section of the report (see below) will show that he has successfully hatched and turned out into the sea about thirteen and a half millions of young flat fish. He reports to me that the spawning fish he now has are in satisfactory condition and that the prospects for the present season are good. The fishermen’s classes were held at the Piel Laboratory in the usual manner and with the usual success. One of the results of the continued success of these classes, and of our natural desire to hold as many of them as is possible in the season, is that our two scientific assistants, Mr. Johnstone and Mr. Scott, are occupied in this work during that period of the year when the principal food-fishes are spawning, when the eggs are appearing in our surface nets and _ other changes are taking place in the floating life of the sea. I feel that it is a distinct loss to us that these naturalists are prevented at that important part of the year from taking almost daily observations from the steamer. When we get, as I hope we soon shall, an increase in our investigating staff it will be very important to have one naturalist at least on the steamer constantly, engaged in carrying on investigations and in recording observations daily. Mr. Scott contributes a section of this report on the results of the Hensen net hauls undertaken in the‘ eastern portion of the Irish Sea between Barrow and North Wales. These results are interesting not only for comparison amongst themselves, station with station and period with period throughout the year, but also beeause eee ee pte a * SEA-FISHERIES LABORATORY. 95 of the considerable differences that they present to the hauls made with the Hensen, Nansen and other forms of net off Port Erin and elsewhere round the South end of the Isle of Man. As Mr. Scott points out, we have during this last year collected and examined more than twice as many gatherings as in any previous year. The Plankton discussed in last year’s report amounted to 400 samples; this year it has run up to nearly 900. The increase is, however, due not so much to work in the Lancashire district as to the very large number of samples which I took with various kinds of experimental nets from the S.Y. “ Ladybird” during the spring, summer and autumn of the past year. The results of these experimental hauls are recorded on 126 sheets, many containing records of from five to ten hauls each. The total number of hauls by means of which we have sampled in this manner the water round the South end of the Isle of Man amounts to about 650. This large series has enabled Mr. Scott and myself to discuss the succession of organisms in the Plankton throughout the year in a limited area, and also the distribution, and relative numbers at different times and places, in a manner which had not been previously possible to us. This is only the beginning of such an intensive study of small areas as will be necessary before we can arrive at any correct estimate of the value and representative nature of such samples. Mr. Buchanan-Wollaston, who has been carrying on fishery work in the University Laboratories, under a grant from the Board of Agriculture and Fisheries, contributes a couple of short papers to this report as the result of his examination of the statistics we have accumulated during the last fifteen years. Although these statistics seem, at first sight, to be large in quantity, H 96 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCTETY. on examination it is found that so many gaps occur in the series that they are not so complete and not so valuable for scientific purposes as might have been expected. It is very unfortunate when a series of observations is deprived of much of its value through some monthly observations having been omitted on account of the steamer being called off to other duties. Every endeavour ought to be made, now that we are starting work with a new, more powerful and more scientifically-equipped vessel, to carry out the periodic observations with punctuality in order that the statistics acquired may be of the greatest possible value—not merely for our own immediate purposes but also for the benefit of future fishery administrators. Dr. H. Bassett, of our University Chemical Depart- ment, has most kindly for the last couple of years undertaken the physico-chemical work in connection with the examination of the samples of sea water obtained on the periodic hydrographic cruises, and he now contributes to this report a paper on his results which is of very great interest; and shows that this work ought certainly to be continued and extended. Mr. Johnstone has been engaged during the year in his usual important work on the bacteriological examina- tion of the shell-fish beds of the district, but is not yet prepared to report further on the matter. He has also been engaged in working up the results of the marked fish experiments, and has continued to devote attention to the parasites of fishes in the district, and we have from him in this report articles on these two latter questions, . to which I need not allude further. I have pleasure in appending to the report this year a comprehensive memoir on Cancer—the Edible Crab, written by Mr. Joseph Pearson, M.Sc. of the Zoological SEA-FISHERIES LABORATORY. 97 Department of the University. Mr. Pearson has been working on this Memoir for several years, part of the expenses of his material being met by a grant from the Board of Agriculture and Fisheries, and part of the expense of producing the beautiful plates which illustrate the structure and life-history of the Crab being met by a grant from the fund for research, placed at the disposal of the University by H.M. Treasury, while the remainder of the cost of the plates will be defrayed by the Liverpool Marine Biology Committee. Mr. Pearson has discussed his subject from practically every point of view and has produced an account of the Crab which will, I hope, be regarded as the authoritative work on this important food-animal, and will, I am sure, be a credit to our report and to the Sea Fisheries Committee under whose auspices it is produced. W. A. HerpMan. FISHERIES LABORATORY, UNIVERSITY OF LIVERPOOL, February 5, 1908. 98 TRANSACTIONS LIVERPOOL BLOLOGICAL SOCIETY. SEA-FISH HATCHING AT PIE. By ANDREW Scort. The results of the hatching work in the spring of 1907 are very similar to those obtained in the previous year. The adult plaice were brought from Luce Bay by the Fisheries steamer and the flounders from the Barrow Channel by the cutter belonging to the northern division of the district. The plaice and flounders commenced to spawn on March 2nd, and the first fertilised eges were secured two days later. The spawning period lasted for two months, and during that period one million four hundred thousand plaice eggs were collected and thirteen million eight hundred thousand flounder eggs. The eggs were incubated in the usual way in the Dannevig apparatus and the resulting fry liberated in the sea. The parent fish were afterwards set free in the Barrow Channel. Towards the end of the year the local fishermen again reported the capture of unusually large plaice from the channel. It is proposed during the present year to find out whether the adult plaice liberated at the end of the hatching season remain in the channel and are eventually captured or entirely leave the neighbourhood. Before being set free a number of the stronger plaice will be marked with the brass label and button as in an ordinary migration investigation, and no doubt the local fishermen will be glad to assist by returning any marked fish that they capture. The following tables give the number of eggs collected, and of the fry hatched and set free on the dates specified ;: — SEA-FISHERIES LABORATORY. Puatcr (Pleuronectes platessa, Linn.). March 4 eel 8 eS § i 14 a, 4-48 meu 22 bger 26 ea April ~~ 1 72 3 -- D 99 8 _ tf a 15 by) 17 a 19 22. te 24 nO :. 29 May 1 Eggs Collected. 12,000 20,000 20,000 40,000 45,000 65,000 65,000 75,000 90,000 90,000 95,000 95,000 95,000 90,000 85,000 85,000 80,000 70,000 60,000 50,000 30,000 25,000 18,000 Total Eggs 1,400,000 Fry Set Free. 1G:0007 2. — Mareh MMOOO, 2 6 hi;900 22), Avril ao,000). ... =i 40,000... rs, DiGIOOt F.. is DAsOOO: «hs. i G69;900., .... ts AD500 ... 1T9,500% —j 5. ‘ 84,500... ie 84,500... Xs 84,000>" -.. — May (D,D00 Ry 2.3 4 (o;0000 ....: x FoLOOO, 22 bs 70;000).. -...2 t 62,000- ..: , H2,5007 22, - 40,000... . 29,000 2 .. s. 22,000 .... . ha500, 42: = 1,231,000 Total Fry 99 100 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. FrLounpER (Pleuronectes flesus, Linn.). Eggs Collected. Fry Set Free. March 4 150,000 133;000.-..... Mareheae rt 6 200,000 177,000 > 2a 3 s 8 300,000 266,000 “- ae = a hae 400,000 300,000 ... April 6 ye lel 600,000 532,000" =e 2 eo abl 600,000 532,000 ‘ 2 Wee /A() 700,000 622,000 sp 13 ea 122 800,000 712,000 M - 2 96 1..< 8005006 712,000 ye a a QO) 1 LO SOK000 846,500 fi 20 Agora 100000 887,000 ie e e Bae LOOCOOS 887,000 iS a Bl By nae SOOOO® 800,000 i. oT bs 8 800,000 712,000 2 2 ant 800,000 712,000 May 4 i ie 800,000 712,000 nd ty ie 17 600,000 532,000 Er: » if 19 600,000 532,000 = Lt uf 22 500,000 445,000 i, bs as 24 300,000 445,000 2 4 hs 26 200,000 177,500 a 18 - 29 200,000 177,500 re .. May 1 150,000 133,000 _ 99 1 3 150,000 133,000 Hp be 5 100,000 89,000 a9 Total Eggs 13,800,000 12,262,000 Total Fry. 15,200,000 13,493,000 Total Number of Eggs Total Number of Fry SEA-FISHERIES LABORATORY. 101 CLASSES, VISITORS, &c., AT PIEL. By ANDREW SCOTT. Following the system that has now been in operation for several years, the Education Committee of the Lancashire County Council renewed the grant which enabled forty-five bona-fide fishermen residing in the Administrative County of Lancaster to attend a course of instruction at Piel in 1907. The Blackpool Education Committee again sent three men, and the Cheshire Hduca- tion Committee six men from Hoylake. The studentship holders were divided into four. classes, three of fifteen each and one of nine men, as shown by the following lists : — First Class, held February 25th to March 9th.—John Randles, Hoylake; Sydney Beck, Hoylake; Thomas Nicholson, Hoylake; J. Bird, Hoylake; William Smith, Hoylake; R. Jones, Hoylake; Daniel Cross, Askam-in- Furness; A. Woodhouse, Morecambe; M. Woodhouse, Morecambe; R. Baxter, Morecambe; N. Sumner, Fleet- wood; W. Cartmell, Fleetwood; R. Gornall, Fleetwood ; H. Johnson, Banks; T. Leadbetter, Banks. Second. Class, held. March Jlth to 22nd—G. Thompson, Roosebeck; T. Stephenson, Flookburgh ; H. Townley, Morecambe; J. Raby, Morecambe; A. Woodhouse, Morecambe; S. Butler, Fleetwood; J. Abram, Fleetwood; W. Leadbetter, Fleetwood; W. Wade, Fleetwood; W. Hardman, Lytham; A. Ander- son, Lytham; EK. Rimmer, St. Annes; W. Harrison, St. Annes; Stephen Johnson, Banks; A. Abram, Banks. Third Class, held April 8th to 19th. Edward Martin, Baychff; Thomas Thompson, Baycliff; Albert Hill, Flookburgh; William Benson, Flookburgh; Albert Threlfall, Morecambe; John Houghton, Morecambe; i= 102. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. John Woodhouse, Morecambe; Robert Bell, Morecambe ; James Butler, Glasson Dock; John Hardie, Fleetwood ; James McMillan, Fleetwood; Joseph Price, Fleetwood ; Hrnest Railton, Fleetwood; John Abram, Banks; Geoffrey Wareing, Banks. Fourth Class, held April 22nd to May 3rd.—David Rawlinson, Roosebeck; James Burrow, Bolton-le-Sands ; W. Lawrence Fawcett, Morecambe; John Burrow, jun., Heysham; William Hargreaves, Knott End, Fleetwood ; John Bridge, Banks; Thomas Melling, Blackpool; Kzekiel Salthouse, Blackpool; Henry Smith, Blackpool. The usual votes of thanks to the Sea Fisheries Committee and to the Education Committee were proposed and carried by the fishermen. Two classes in nature study for school teachers were held during the months of April and May. The classes were organised by the Barrow Kducation Committee and were attended by teachers belonging to their schools. The course of instruction for school teachers has, on the suggestion of Mr. A. Haveridge, Director of Education at Barrow, been somewhat modified and re-arranged. The course has been divided into three stages. The first deals with the common organisms of the sea shore between tide marks, and the general animal and plant remains from the sea bottom washed up along high-water mark. A brief account of their distribution, habits, and uses is given, and an explanation of the methods of collecting, preserving, and mounting natural history specimens for school museums. In the second stage certain common types of marine animals are studied more fully than in the first course. These types include a common fish like the codling or herring, starfishes and sea urchins, common shore crabs, cockle, mussel, &c. The third stage deals with microscopical preparations, the use of the tow-net, SEA-FISHERIES LABORATORY. 103 microscopic life in the sea, and the life-history of some common type of marine animal. A large party, consisting of representatives of the Sea Fisheries Committee and the various Educational Committees of Lancashire, visited the laboratory on April 24th and saw the fishermen at work. An interesting address on the scientific and educational work of the Sea Fisheries Committee as apphed to fishermen was given by Mr. A. T. Wright, and was greatly appre- ciated by the audience. Mr. Walter HE. Archer, Assistant Secretary to the Department of Agriculture and Fisheries, inspected the establishment in April. Mr. M. A. Fenton, one of H.M. Inspectors of Schools, visited the laboratory to inspect and report on the work of the classes for fishermen and school teachers A good deal of time has been devoted to the examina- tion of the pelagic organisms in the Irish Sea around the Isle of Man, and from there to Lancashire and to Car- digan Bay, which were collected by various kinds of nets at depths ranging between the surface and 60-70 fathoms. In fact, 1907 makes a record for this part of our work. In 1906 the number of plankton samples collected and examined was just four hundred, while in 1907 that total was fully doubled, as is shown by the following figures : — Ordinary tow-net collections by the Fisheries steamer res yon 1 160 Hensen Net, monthly observations ae Pa Fishery officers in Cardigan Bay, ordinary tow-net 60 Samples taken by various nets around the Isle of Man by Professor Herdman, and in Port Erin Bay by Mr. Chad- wick and others og 638 Collections made round the Wiest oe Scotland by Professor Herdman _... 10 Total. 2 ee is 400 104 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Owing to the necessary arrangements in contempla- tion of the sale of the former Fisheries steamer and the Captain Wignall’s collections could not be so systematically made b] delay in delivery of the “James Fletcher,’ as in former years, and the number is naturally reduced in consequence. ‘The results of the monthly observations with the Hensen net and of the extensive series of collections taken by Professor Herdman from the S.Y. “ Ladybird,” are dealt with elsewhere in this report. The other collections are in process of being worked up, and reports upon them will be given later. SEA-FISHERIES LABORATORY. 105 MONTHLY INVESTIGATION OF THE PLANKTON BY THE HENSEN NET METHOD. By ANDREW Scort. This investigation was commenced in January, 1907, with the intention that regular hauls should be taken at intervals of one month, between Piel Gas Buoy, at the outside entrance to the Barrow Channel, and Great Ormes. Head, on the North Wales coast. Owing to unforeseen circumstances the continuity of the observa- tions was interrupted on three occasions: no hauls were taken in April, July and December. In the absence of a complete series of monthly observations it would be unwise in the present report to discuss the changes that take place, from month to month, in the pelagic organisms along the line of observation. At the same time, one or two interesting facts can be detected by a review of the tables of results given below, which are worth some attention. Three stations have been laid down along an imaginary straight line, joining Piel Gas Buoy to Great Ormes Head. The first station is four and a half miles, the second twenty-two and a half, and the third forty and a half miles from Piel Gas Buoy. The third station is four and a half miles off the Orme’s Head, and the middle station is eighteen miles equidistant from the first and third. At each station the ship is stopped, and when all way is off her the net is put over the side, lowered down to a depth of ten fathoms and then slowly drawn to the surface. The time taken to draw the net up through ten 106 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. fathoms is about sixty-five seconds. The net is then got on board and the ship continues her course to the next station. As soon as the net comes on board, the contents of the metal bucket, provided with a tap at the end of it, are run off through a fine silk filter of the same texture as the net. The tap is then shut and the outside of the net well washed down with the ship’s hosepipe. In this washing of the net, the bucket is again filled with the water that passes through the silk, and any organism adhering to the inside of the net after the first straining are taken into the bucket with the washings. ‘The contents of the bucket are again passed through the silk filter and the whole catch and silk of the filter are at once transferred to 3 per cent. formalin in sea water and labelled. The samples are afterwards carefully examined ashore. For an explanation of the methods now adopted in the investigation of our plankton samples, see the joint report on the plankton taken off the Isle of Man by Professor Herdman and myself. The first point to be noted, is that the amount of life in the sea during the early months of the year is very small, from May on to September there is a great increase in bulk, and then towards the end of the vear it falls away. ‘The nine hauls taken in the first quarter of the year gave nineteen cubic centimetres of organisms, while the three hauls taken in September caught eighty cubic centimetres altogether. Next, taking the organisms in order, we find that in January, Diatoms were scarce and only represented by two species. In February a considerable increase in numbers was found and thirteen species were present along our line of observation. A further increase was found in March and twenty species were noted. Diatoms further increased in May and the species represented reached a SEA-FISILERIES LABORATORY. 107 total of twenty-six. In June, although the species present had fallen to nineteen, the number noted was high, and the bulk of the plant life consisted of Mucampra and Rhizosolenia. In August and September the Diatoms continued to be very abundant and the species represented were nearly as numerous as in May. In October there was a marked decrease in numbers and the species had fallen to twenty. An apparent recovery was found to have taken place in November, and the number of Diatoms taken in the three hauls was fully twice that found in the three hauls for October. During October and November there were more Diatoms in the vicinity of Walney than at the other two stations, and the central region contained the least. It will be noted that the hauls taken in October yielded 34, 17 and 5 cubic centimetres of organisms respectively, yet the numbers of Diatoms were completely inverted, as the following figures show: (53) 24°300; (17) 7450; (5) 12°700. Species of Ceratiwm were present in eight out of the nine monthly hauls. They appeared to be entirely absent in the whole area in January and at Station I in February. It will be noticed from the tables that from the month of June to the end of the series, these organisms were more abundant at Station I than at either the second or third. It is evident that there is a distinct maximum period in August. Specimens of Peridiniuwm were much scarcer than those of Ceratiwm, and apparently reached their maximum point a little earlier in the year. Noctiluca has been recorded in our reports for some years as occurring in large numbers along the North Wales and Lancashire coasts during the summer and autumn months. The specimens found in the hauls for January, February and March were probably survivors from the a 108 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. summer of 1906, as none were observed in May. ‘The organism was present at all the stations in June, and in large numbers again in August and September. The hauls taken in October showed a decided decrease, which became still more marked in November. It is probable that the maximum point of the invasion was reached about the end of August. The bulk of the samples taken in August and September consisted of Noctiluca. Specimens of Sagitta were present in the area in each of the months that collections were taken, and only once appeared to be absent from any of the three stations. The largest number of specimens were taken in September. Copepoda apparently follow pretty much the same increase as the other groups, and the largest numbers were found in the September hauls. When a complete series of hauls with the Hensen net along this line is available for comparison, it will be possible to discuss more fully the changes that take place from month to month amongst the organisms that make their appearance in the upper layers of the sea throughout the year. SEA-FISHERIES LABORATORY. 109 Station and Date.—Hensen Net Stations, January Sth and February 5th, 1907. Depth in fathoms ......... 10-0 10-0 10-0 10-0 10-0 10-0 oS DC 2 3 2 2 3 p 2 TUS eee ee i Il. IBD I. JU Il. Asterionella bleakeleyi — — = = — 25 Biddulphia mobiliensis...... — — 8 800 570 800 Chetoceros decipiens ...... — — — 600 200 100 Coscinodiscus concinnus ... 25 6 58 500 500 550 = PEM Fe, — —_ — 24 20 — Ditylium brightwellii ...... — = == 30 — — Melosira bDOrreri ............ — == — 8 = — Rhizosolenia semispina ... = = — 30 30 100 5 SEbISETS, - ...... = = 7 20 10 — zs shrubsolei ... — — — — — 25 acillaria paradoxa ......:.. — = = 12 = 100 Bellerochea malleus ......... — — — 15 3 — Nitzschia closterium ...... = = = = 10 75 BEMEMMSCIA SP. ..2....ssce0ee. = = = = — 25 Beeatium furca ...........5.+. — — — — 10 50 a STIS ns — -- — 20 100 a (3:01 eee eee — — = = 200 50 Noctiluca miliaris............ 1 30 100 14 10 = Pleurobrachia pileus ...... = = — = — 1 Sagitta bipunctata ......... 8 12 56 5 37 8 Larval Polycheta ......... 1 = 3 — — — ECMEL SD) iA teases siesie ecco — — 1 _ 30 — Mysis stage of Crangon ... 3 — — — — = -Microniscus calani............ = — 4 _ — — Calanus helgolandicus ...... 1 1 — — = = Pseudocalanus elongatus ... 72 30 135 54 3 36 Temora longicornis ......... = — — 2 3 Centropages hamatus ...... = = 7 = — 4 SeeatEtia ClAUSI .....0..s00000. 6 5 18 23 20 13 BMOHA SUMINS ...........002 3 ] 5 94 70 90 Paracalanus parvus ......... 35 16 119 52 25 15 Thompsonula hyena ...... — = — 3 — — Copepod nauplii ............ — — — 60 1,290 150 Lamellibranchs, larval...... — — i = = — Scopleura sp. ...........01+- 1 — — — — a BeeeIdian CFOS .........2.0.5- 1 — — — _ — 110 1907. Depth in fathoms Catch in ec.em. Station Asterionella bleakeleyi Biddulphia mobiliensis...... Cheetoceros contortum decipiens sociale 35 teres ie subtile Coscinodiscus concinnus ... weer eee seer eee seers eeeee 99 AUT PELL teens eeeeseeee eeeeeseeesee eeeeetoee TRANSACTIONS LIVERPOOL BIOLOGICAL Kucampia zodiacus ... Rhizosolenia setigera 99 ecvces shrubsolei ... Actinoptychus splendens ... Biddulphia aurita ... NEW IADIS) Soap 99 a granulosa Coscinodiscus radiatus Leptocylindrus danicus Bacillaria paradoxa Ceratium’ fureay...s..s-eeee. - CEUPOSSsteasenen sce Rericimyamn Same src eee Noctiluca miliaris ............ Pleurobrachia pileus Medusoid gonophores ...... Sagitta bipunctata Larval Polycheta SMitraria, thee ecu Os 5 a Podon intermedium:.....-- Pseudocalanus elongatus ... Temora longicornis ......... Centropages hamatus ...... Acartia clausi Oithonarsimallistys essen. Paracalanus parvus ......... Cyclopina littoralis Copepod nauplii - metanauplii m juv. Barnacle nauphi Lamellibranchs, larval Oikople usa Si vs cci0 02 oe eee eeeeos eerccccce eceesecos SOCIETY. Station and Date..-Hensen Net Stations, March 5th, — > : SEA-FISHERIES LABORATORY. Hale ' Station and Date.—Hensen Net Stations, May 10 and June 5, 1907. Depth in fathoms Catch in ¢.cm. Stations Asterionella bleakeleyi | japonica Biddulphia mobiliensis...... Cheetoceros contortum : were ser ere see seeeeeeeee . debile = .....6.5. a @eei piers) —-.. 4; - densum ......... ms sociale *.......:. a KEKEST a. secemeeees a SWOtWe sic...c5. diversum ...... Seeeinadiscus concinnus ... GLAM os 52. 205 Coscinosira polychorda Ditylium brightwellii Eucampia zodiacus Melosira borreri ............ Rhizosolenia semispina ... eereccene a Ssetigera <2... a shrubsolei ... * stolterfothii... Biddulphia aurita ......... Ee granulosa ...... -Coscinodiscus radiatus...... Bacillaria paradoxa ......... Guinardia flaccida............ Lauderia borealis ............ ‘Streptotheca thamensis ... meeatium furca ............... ‘. ST CUS a er MENDIOS Sooo ee eas Peridinium sp. Mrochiscia sp. ......0. setigera a shrubsolei ... Lauderia borealis ............ Bacillaria paradoxa ......... | Bacteriastrum sp. | Biddulphia rhombus ss granulosa 7 favus Coscinodiscus granli........., os radiatus ...... Guinardia flaccida............ Weratium furca ............... a ROUSE ce le oe. cio.0 a tripos MMexasterias Sp. ........+...+-- | Trochiscia sp. SMILINNOPSIS SP...........-.6- Noctiluca miliaris Pleurobrachia pileus Medusoid gonophores Plutei of Echinoderms Sagitta bipunctata Autolytus prolifer Larval Polycheta 0 Cie | Crab zoea PE MNCOAIOPA: -220220+-020006 Mysis stage of Crangon ... Calanus helgolandicus Pseudocalanus elongatus... Temora longicornis Centropages hamatus Acartia clausi Oithona similis Paracalanus parvus ......... Isias clavipes Euterpina acutifrons Copepod nauplii 8 juv. Gasteropods, larval Lamellibranchs, larval ...| Oikopleura sp. __............ | Mescidian CPPS ..........0006- eeeeesessees weer eres eees) | eeeeoe, eesees Seer reer eseesseeseeses ee eee eee eee sees se ee eee esse sees eeeres oe esenees Fi Se i LABORATORY. Station and Date-——Hensen Net Stations, October 7th 1138 750 8,650 50 100 300 10,000 1,750 100,000 —_ 250 4,250 150 75 190 75 225 975 2,700 250 1,300 1 10 375 1,720 75 1,335 or ell lsalalelsl! | er) 114 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. REPORT ON EXPERIMENTS WITH MARKED FISHES DURING THE YEAR, 1907. (Plates I and II). By Jas. JOHNSTONE. It was only possible, for various reasons, to continue these experiments during 1907 on a less extensive scale than during 1905-6. We resolved to concentrate the experiments as far as possible, and to confine our attention to the summer plaice fishery in Liverpool Bay, and to the autumn and winter plaice fishery that is carried on in Red Wharf Bay and in Channel Course. Three experiments were therefore made, (1) in Menai Straits in February, 1907, when about 100 small plaice were caught by the “John Fell” and liberated close to the place of capture; (2) near Nelson Buoy at the entrance to the Ribble Estuary in July, 1907, when about 150 plaice were caught, also by the “John Fell,” and lberated on the ground where taken; and (3) in Red Wharf and Beaumaris Bays in October, 1907, where 120 plaice were caught and liberated. I intended to mark and liberate plaice and flounders in the neighbourhood of the Lune and Wyre Rivers, and in Barrow Channel, but did not find this possible because of the other engagements of the “ John Fell” and the Fleetwood police cutter. In June a number of plaice which had been kept during the preceding year in the spawning pond, at the Port Erin Hatchery, were turned out into the sea, and at Prof. Herdman’s request I sent a number of labels to Mr. Chadwick, Curator of the Biological Station, who then marked 28 large plaice and liberated them near Bradda Head. During 1907 we, therefore, marked 360 fishes, all plaice with one exception, and at the time of writing (16th > SEA-FISHERIES LABORATORY. LS December) 102 of these have been returned to me. In addition to these fishes 47 others marked and liberated during 1905 and 1906 have also been returned, making 149 recaptures in all. No attempt was made to mark other fishes than plaice during 1907, but we hope in the coming year to devote some attention to flounders. As in former years, 1 am convinced that quite a number of marked plaice are captured and are not reported to me. One hears, now and then, of fish that have been captured for some time, and it is curious that over and over again marked plaice are recaught by the same boats. One could draw up a list of smacks that have caught what is apparently far more than their share of marked fishes, and I am inclined to suspect that many fishes, caught perhaps during the dark, are not noticed. Most of the fishermen on the West Coast of England must now know about these experiments, but it appears that until a skipper has caught one or more marked fish he and his men do not examine their catches so carefully as to avoid the risk of a marked fish going unnoticed. As before, I am greatly indebted to those who have taken the trouble to send me marked fishes handed to them. This applies particularly to Messrs. Harley and Miller, of the Liverpool Fish Market, Messrs. Dean and Houldsworth (members of the Committee); Mr. Robert Knox, of Douglas; and Mr. A. J. Rust, of Milford Haven. Captain Jones, Head Bailiff at the Carnarvon Station, has also taken a great amount of trouble to forward me all fish given to him, and has been most careful in supplying all the necessary information of recapture, &c. I give all the details of recapture in the tables that follow. The “general summary” gives the total results of the experiments of the year, and includes, also, marked fishes which have been liberated in 1905 and 1906. The 116 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. following tables give the details of recapture and growth of the fishes returned. ‘The “analyses of sizes of fish recaught ” give the numbers of plaice of each size group (every quarter of an inch) marked and liberated; it will be seen that the majority of the plaice dealt with were between 9 and 11 inches in length. In the tables of “particulars of fishes returned” the columns are numbered in order to save space. The headings are :— | a | | Ee nf oS Ss oy o = oO) oS — 3° 2 See | 1 8B os o5 no Sa e| Boo | ae o o~ 12 mM o ~ CS o a mac) oc ° sf BSS Qo ~~ Q <=) aS ao) & oo re iz & eve | £8 BS se S5as|S22| S8 S22 |] ao AS Os jt os) Eee | OF ans Ey = | a = = The lengths of the fishes when marked were measured to the nearest quarter of an inch. The lengths when returned were measured to the nearest eighth of an inch. When only one or two fishes are returned in any particular month an error may result from this difference in the accuracy of the two measurements, but when average growth-increments are calculated, and when these are plotted on a curve, and the latter smoothed, such inaccuracies disappear. The place of recapture is usually given as reported to me. It is generally unlikely that it is accurate to within a mile or two, asa fish may be caught anywhere during a drag of the trawl-net, which may be of 20 or more miles in length in the case of a steam trawler. As a rule, however, such inaccuracies in position have no real significance. The values, ‘months in the sea,” have been obtained by subtracting the number of the month of liberation from that of recapture: they are calendar months. The letters under heading 8, ‘“‘ method of recapture,’ denote: —ST, steam aueial SEA-FISHERIES LABORATORY. Gwe trawler; 1T, Ist class trawler; 27, 2nd class trawler ; SN, stake net; TN, trammel net; DN, draw net or seine net. The greater number of the fishes returned were recaught by means of trawl nets used by Ist and 2nd class trawlers. In some cases this information as to the method of recapture was not given; in one or two cases it was also impossible to trace the position of recapture. Whenever possible the fishes were weighed, but very often they had been gutted before being forwarded, so that it was not practicable to estimate the weight in every case. In the case of every fish sent, the otoliths were removed, and are being kept with the object of determining the mode of growth of these structures in relation to the season. ‘ATMO squUOTILIedxo YSTOAA PU OATYSBOURTT WIOA, poyepNoTeD | "sqJsBood YSPOM pUR aLLYSvOURTT oYY UO poyeroqity soysy oyy ATWO sopnypouT -. ag Rae te - wa oxaiie aaa “oT en PR eh aed OR terincannaticg, | Z = sl peal a cece ae ccs: sernssraceneerssnnterr=sorsae QART 40 SIMaoRTOEa | 1e.9z | ZOT | xO9E avatelalolsietatelolaleletaie|(alel svelalelsielalela(ale¥eloislale(elelslalalalelalaslole LOGI Jo syuotIIed xy ‘sTeqOg, 8.08 | 1¢ | aoreyd OZI 10/01/#2 Bia Vorer ahs’ se aca har tcl cteWale claterel causa Ciace rcica cheerclac ata teitiete keg sleumneeg 5 | Tq T G-FZ 9¢ SOC! Nia | MOAI eens qqAqYy 07 souvsjug ‘Aong wosfeN TeeNy | ¢ = ae aoretd gg | L0/9/T |" WRI JO EIS] “peoH epperg wory -N sop ZZ TRANSACTIONS LIVERPOOL BIOLOGICAL Ge 66 sored ZG 10/2/9 ; HOOD 00 O0GUONODG0O000 Sq}IBIY TRUOTA, 0} souRIqUy uleysey I ‘pouin é A eeeee Bans “poyeroquy “ON “OVeC “peyesoqry sSoysty o1oyM ooV[dq ‘CHNYNLEY ANY CGHLVYHPIT SHHSIW HO SYHANON ANV SNOLLYVLS — AYVAWNOS TIVEHNHD 118 SEA-FISHERIES LABORATORY. 119 DETAILS OF FISHES RETURNED. Experiments of 1906. The following fishes, returned in 1907, are to be added to the lists given in the last Annual Report. meperrment 2, 9th February, 1906. Station: Near Fleetwood. 39 plaice. L752 11} Off Dundalk, E. coast of | 26/11/06) 9 | 14 23) SE Treland L768 11 NOG KNOW, . 06. escpecenacces 8/3/07 | 18 | 152) 42); — eae L769 9 14 miles E. from Corse- | 18/4/07 | 14 | 11 wall, Clyde, 12 faths. | The results of this experiment were discussed in last years Report, but several recaptures have been made during the present year and some doubtful cases have been traced. It may be useful, therefore, to summarise the results anew. IlHighteen of the 35 plaice hberated, or over 51 per cent., have been returned, and it will be seen that the positions of recapture are distributed over a considerable area, one fish being taken in the Firth of Clyde, and one off the Kast Coast of Ireland. It will be noticed that a group of eight fishes have been recaught in inshore waters during the four months after the date of © hberation. Two of these had migrated to the South, but were recaptured still in shallow water inshore, while six fishes were taken in almost the same place where those hberated were originaily caught. Then we have a group of seven fishes recaptured much further offshore and in relatively deep water, and all from seven to ten months after the date of liberation. Finally, three fishes are included in this year’s recaptures: one taken near Dundalk, one in the Firth of Clyde, and one taken probably by a steam trawler not far from Morecambe 120 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Bay Lightship. On Plate I these three latter. recaptures are indicated by large round spots. I think that the results of this experiment indicate those that might be expected if it were practicable to mark and liberate a very large number of plaice on the inshore grounds during the early months of the year, that is, that these fishes would remain there until the end of the spring, to be caught by the stake-nets or inshore trawlers, and then, as they began to experience the season’s growth, they would gradually move offshore into deeper water, and would not again return into the shallow bays and estuaries. Unfortunately, it is not easy to obtain a sufficiently large number of small plaice by trawling in the estuaries during January and February, and I can only suggest that the fish should be caught by stake-nets, and taken alive into Piel Hatchery to be marked. Experiment 0; oth March, [ogee Station: Near Blackpool. L948 | =13F Lune, near No. 3 Buoy | 21/9/07 18)?14 1) DN L949 | 133F | Near Arnside, Morecambe | 21/8/07 | 17 | — | — | — Bay. L953 93 20 miles N.E. from Ba- | 11/5/07 | 14 | 143) 43) 1T hama Light Ship, 24 fathoms. | L971 83 5 miles E. from Bahama | 30/5/07 | 14 | 11%, 32 ST Light Ship. | L980 11F « Pombrot Shoals! io. + ,25/3/07 | 12 fe 14| ST Experiment B. 6th March, BO OG Station: Colwyn Bay. 1 2 3 4 5 | 6 LL21 81 K. from Bahama Light. | 19/4/07 | 13 | — LL38 81 Red Wharf Bay, 12 | 14/12/06) 9 | 102 fathoms. SEA-FISHERIES LABORATORY. Pxpenrment Sj i3lst March; Lo 0. Station: Outside Walney Island. 1 2 3 4 5 | 6! 7) <8 LL103 73 5 miles §.S.E: from Ba- | 21/12/06} 9); 92 2) ST : hama Lightship. Boaperiment 10), [2th June, 1906" Station: Near Nelson Buoy. Ee 3 4 5| 6|. 7/8 __ | ee a ee eae ee PUREE ORY Fs Asters pets Conse (22 ca | | LLI86 | 84 | 15 miles off Coningbeg | 6/7/0/7 | 13 | 123) 43) 1T | | Lightship. LL187 91 | Off Eastham, River Mer- | 19/12/06} 6 | 113; 14) 2T | sey, 11 fathoms. LL190 OF i} Not KNOWN. 2.00 ..gsc0ve0 use 22/1/07 | 7} — | — | — LL192 8? 6 miles 8. from Bahama | 22/12/06; 6 |710 1 ST | Light Ship. LL198 84 | 10 miles 8.S.E. from Mine | 17/3/07 | 9 | 123} 42) 1T | Head, S. coast Ireland, | 38 fathoms. LL204 82 | S.W. from Caldy Island,! 1/8/07 | 14 | 123) 3% 1T 26 fathoms. | Pupercement to, 9th July, 1906; Station: Near Nelson Buoy. 1 2 | 3 a 5:6.) anes LL261 | 81 Off Kinsale Head to S.E. | 8/4/07 | 19 | 103] 22 ST by E., 46 fathoms. | LL266 gt Off Nelson Buoy, 9 faths. | 12/6/07 | 11 | 103) 14, 2T LL269 9 Off Caldy Island. ....... eel AfijOd | 12°) Li erin LL276 83 4 miles N.W. from Nelson | 12/6/07 | 11 [710 14) 1T Buoy. LL280 9 6 miles 8.S.W. from More- | 23/7/07 | 12 |?13 | 4] 1T cambe Bay Light Ship. LL289 81 6 miles 8.E. from Bahama | 9/12/06 | 5 | 103) 23) ST Light Ship LL297 81 | 2miles E. from Liverpool | 7/7/07 | 12 | 102) 23) 1T | Bar Light Ship. 121 122 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The results of Experiments 10 and 15 of 1906 also confirm the conclusion that the plaice reared on the: Lancashire shallow water grounds move offshore with increasing age and do not return. The recaptures in 1907 from these two experiments are indicated on Plate II by the black spots, and it will be seen that of the plaice liberated in 1906 near Nelson Buoy only two were recaught on nearly the same grounds in 1907. On the other hand, two of these plaice were recaught in 1907 to the S.1d. off Maughold Head; and six have been recaught off the 8.E. coast of Ireland. All the latter are, compared with the plaice recaught off Nelson Buoy (the ground of original capture), large fishes. One fish, the imevitable exception to the others, was found in the River Mersey, as far up as Hastham. Experiment ll; Idth June, Wome Station: Near Pwllhel1. 1 2 3 4 5 | GoLive LL208 93 S.W. from Godreooy, S. | 15/2/07 | 8 | 12}; 234) — coast of Ireland, 20 fathoms. This fish is one of a lot of 40 set free in Tremadoc Bay in the summer of 1906. So far, only three fishes have been recaptured; one near the place of liberation, and two off the Irish coast. Experiment 12, 14th June,—lGie Station: Off Llanrhystyd, Cardigan Bay. LL247 114 10 miles 8. by W. from | 7/7/07 | 13 | 12 4| ST Coningbeg Light Ship, 38 fathoms. LL334 84 4 miles W.N.W. from | 26/4/07 | 10 | 9% 1} 1T Aherayron, Cardigan Bay. LL337 72 Carmarthen Bay, 3-4 18/4/07 | 10 | 94} 13 fathoms. SEA-FISHERIES LABORATORY. 123 Paopermment 13% 16th June, 19:06; Station: Off Dinas Head, Pembrokeshire. a sc ms i i in | i | | ss | es LL356 a 4 miles N.N.W. from | 20/4/07 | 10 | 14] 0O| 1T Aberayron, Cardigan Bay. LL351 132 Newport Bay, 7-8 faths. | 5/6/07 | 12 | 143} 1 | 1T Epeperimend 162 12th’ Jwiy, 19 0i6- Station: Off Penkilan, Tremadoc Bay. 1 2 3 4. 5| 6) 7| 8 LL411 83 Near Caldy Island, 20 | 10/9/07 | 14 | 11%) 34) 1T fathoms. LL415 9 Pinfold Channel, 2 faths. | 18/1/07 | 6 | 103} 13) 2T LL434 Si Dinas Head, bearing | 22/6/07 | 11 | 11 | 23) ST W.S.W., 12 fathoms. Peeperiment i/, loth September, 1306: Station: Red Wharf Bay. 1 2 3 4 5| 6 LL440 111 2 miles from St. Patrick’s | 22/10/07) 13 | 142) 334) H Island. | LL446 104 Red Wharf Bay.. 10/1/07 | 4| — | — | HN LL450 102 Holyhead Outer Harbour 25/1/07 4/111; 3, TN LL457 10 Conway Bay, 7 fathoms. | 20/10/07) 13 | 134) 32) 1T LL459 gl Menai Straits .............5. 5/3/07 | 6 | 93) 4| 20 LL463 10 Holyhead Outer Harbour.| 12/1/07 | 4 | 103) 3) TN LL465 9 ed Whart ay .os0--e--s -- 19/12/06) 3 | 93 3) IT These recaptures are indicated in Plate I as red spots. It will be seen that six of the plaice in question 124 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. have apparently remained in the neighbourhood of their original place of capture. Five of them were caught at the beginning of this year, or at the end of last year, but one was taken in almost the place where liberated a complete year afterwards. One had crossed the Irish Sea, and was caught off the coast of Ireland. Experiment 18, 3rd October sea Station: Luce Bay. 1 2 3 4 5 | “6st LL493 12 duce Bay. ava eater | 7/5/07 | 7 | 123} 3|DN LL497 121 Tuce ABay wes cr te oe eer eee | 19/7/07 | 9 | 13th sisi LL500 11t 15 miles 8.E. from Maugh-| 27/2/07 | 4 {| 114) 0} 1T old Head, I.O.M. LL505 134 (?) Off Dhu Hearteach,| 25/4/07 | 6 | 134} 0} ST W. coast of Scotland. LL517 13 Near Denure Harbour, | 20/11/07/ 13 | 153} 23; — * Firth of Clyde. | These recaptures exhibit nothing noteworthy. Plaice No. LL506 is recorded just as received, though I think it extremely doubtful whether the information as to ue place of recapture is accurate. Experiment 21, Idth October, ee Station: Luce Bay. SEA-FISHERIES LABORATORY. 125 The following fish was reported to me, but the label (which alone was sent) was entirely corroded away, so that only the silver wire and the bone button were attached to the fish when caught. It is probably one of the Luce Bay fishes hberated in 1904 or 1905. | a |) Gare eas | cE eee ee ee | eens eee | a see ae a eee na | — — 4 miles 8.W. from Girvan | 7/1907 | — | — | — | — Harbour, Firth of Clyde. | Experiments of 1907. Eeeperimemt 1 bth-~ February, LOO, Station: At Eastern Entrance to Menai Straits. All the fish caught in Menai Straits, and in Beaumaris Bay. ANALYSIS OF St: ES oF Fisnes LIBERATED. BEEZ CHES 550,005) 5inn wisi ics ate v0 bine 7i| 74; 72) 8 | 82 84 82] 9 NEE Oe PEAICO) 2 ont ae bee's oc esdie aos hn vee 2 3 9/10} 14] 11); 10 | 10 Sie (Pe 7 a ae, Ae ee sO 91 92) 93) 10 | 104] 103} 11 | — Merratarttics thes eects exe Sade WeGel oe on ld ie 126 LL595 LL596 LL598 LL651 LL652 LL653 LL657 LL658 LL659 LL660 LL663 LL664 | LL667 LL668 LL669 LL673 PARTICULARS OF Fisutss RETURNED. 5 miles N.W. from Jumbo Buoy, 9 fathoms Off Holyhead Breakwater, 8 fathoms. Dinas Head, bearing W.S. W., 12 fathoms. Carnarvon Bay 8 miles 8S. by W. from Morecambe Bay Light Ship. Off Friars, below Beau- maris, 3 fathoms. Penrhyn Fish Weirs, Menai Straits. Red Wharf Bay Between Newcome Knoll and Deposit Buoy, Entrance to Mersey. ee) Between Point Lynus and - Great Ormes Head, 15 fathoms. Conway Bay, 7 fathoms. Between Point Lynus and Great Ormes Head, 15 fathoms. Between Beaumaris and Gallows Point, in Menai Straits. Carnarvon! Bay aineccesesee 2 miles N. from N.W. Buoy. Red Wharf Bay, 10-11 fathoms. 8 miles N. from More- cambe Bay Light Ship. Off Deposit Buoy, 5 fathoms. Red Wharf Bay, 11-12 fathoms. Between Point Lynus and Great Ormes Head, 20 fathoms. 5 miles W.S.W. from Nelson Buoy Off Dinorwic, Menai Straits Red Whart Bay c-tte.css-: Red) W hart, Bayo. ma-cene- Off Beaumaris Pier, 4 fathoms. 10-20 miles S.E. from Bahama Light Ship. Between Beaumaris and Gallows Point, in Menai Straits, 3 fathoms. 2 miles N.W. from W. Constable Buoy, 13 fathoms. Lavan Sands TRANSACTIONS LIVERPOOL BIOLOGICAL 12/6/07 30/3/07 20/6/07 13/6/07 | 22/8/07 | 30/11/07) 11/5/07 | 5/12/07 | 11/10/07, 14/11/07] 2/11/07 23/10/07 14/3/07 13/6/07 11/6/07 3/12/07 27/2/07 9/9/07 3/12/07 12/11/07 27/9/07 1/3/07 4/10/07 8/12/07 25/10/07 20/7/07 14/3/07 7/7/07 16/10/07 o-~r Ww O-~18 lo) 10 oie) SOCIETY. pte CANS SEA-FISHERIES LABORATORY. 127 Thus 92 plaice were liberated in the entrance to Menai Straits in February, 1907, and at the end of the same year 29, or about 31} per cent., have been returned. The results of the experiment are represented in Plate I, and it will be seen that the recoveries fall roughly into three eroups: (1) four fishes caught in Menai Straits during the four months after the date of liberation; (2) eight fishes caught in Liverpool Bay during the summer and autumn ; and (3) a group of ten fishes caught in Red Whart Bay and Channel Course during the late autumn and winter of 1907. One fish was taken in Holyhead Outer Harbour in a trammel net, two fishes were caught in Carnarvon Bay in June, and one fish went as far South as Dinas Head in Pembrokeshire, where it was caught, also in June. Immediately after liberation one fish migrated to the North, and was recaught not far from Morecambe Bay Light Ship. Peeporiment 2, lst June, 13907. Station: Two miles North from Bradda Head, Isle of Man. The plaice marked in this experiment were part of the stock of “ spawners”’ kept during the preceding winter and spring at the Port Erin Hatchery. ANALYSIS OF SIZES OF FisuEs LIBERATED. . . | LE) ee 12 | 123) 123) 13 | 134 133, 133) 144 MptOE pide. 5.00ccdices.deecec seo xe Pi |) me a Co a iy ag MP As lie has (Ee re ee 14t 151} 154| 153| 16 | 163] 19 | 194 Oe OL 2 Es eee Bee eo 1 1 1 1 1 K “a 128 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. None of these plaice have yet been returned. The fishes were marked and liberated by Mr. H. C. Chadwick, of the Port HErin Biological Station. I think it possible that the fishes were enfeebled as a result of long confine- ment in the spawning pond, and did not survive the mark- ing operation and subsequent handling. Experiment Station : Estuary. 3, Fish caught near Nelson Buoy. ANALYSIS OF SIZES OF ord dine Near Nelson Buoy, Entrance to Ribble Loos Fisnrs LIBERATED. Size s(imelies) |i te-4.n-e-- eee oe 74] 74} 72) 8 | 84h 83) 82 OF Of INO of plaice jeesceeeeere: 1 |) 1 | 8 | 19 | °25-) 245) 1S eee INO: ofwlorilltc.s.u.cca cee. —}—}]—);—!/—]— The — Size a(n hes) siete eee eee 94; 92) 10 | 104) 103% 11 | 113; 113} — No. ofplaice, peek aeatee 15) 2\:9| 84-3] 2) 2a INO: Of ibrili a sii ws.ccteee aceeecr —}|—}—}—!—}] ly—j|—f — ParTIcuLARS OF FisHEs RETURNED. 4 2 3 4 5| 6 | 75/58 LL689 94 Ribble Bar, 6 fathoms, | 2/12/07 | 5 | 103; 3% 2T H.W. LL691 8h 6 miles N.W. from N.W. | 11/10/07; 3 | 10 | 1% 2T Buoy, 6 fathoms. LL695 10} Heysham Lake, in shal- | 22/8/07 | 1 | 11 3; DN low water. LL696 8 1 mile W. from Jumbo | 10/11/07; 4 | 10}, 24) 2T Buoy, 64 fathoms. LL704 7% * Morecambe Bay” ...... 11/8/07 | 1| 83 #2 IP LL709 114 Off Nelson Buoy, 17 faths..) 14/8/07 1}; —|—|1T LL711 10 7 miles N.W. from Liver- | 4/8/07 | 1 | 103} #3 1T pool'N.W. Light Ship, 15 fathoms, 4 ~~ LL713 LL717 LL720 LI 726 LL730 LL732 LL737 LL752 LL758 LL763 LL764 LL767 LL768 LL772 LL781 LL782 LL783 LL792 LL799 LL806 LL810 LL813 LL814 LL817 LL820 LL822 LL823 LL824 LL827 SEA-FISHERIES LABORATORY. 3 miles W. from Nelson Buoy. ‘| Liverpool Bar Light Ship bearing S. by E., 15 miles distant, 15 faths. 2 miles S.W. from Nelson Buoy, 10 fathoms. 12miles N.W. from Liver- pool Bar Light Ship, 15 fathoms Off Nelson Buoy, 14 faths. Roosebeck, Morecambe Bay. 10 miles N. from Liver- pool Bar Light Ship, 14 fathoms. 3 miles N. from N.W. Buoy, 6 fathoms. Off Nelson Buoy, 17 faths.. 5 miles W.S.W. from Morecambe Bay Light Ship. 10 miles N. from Liver- pool Bar Light Ship, 15 fathoms. 2 miles N.W. from N.W. Buoy, 6 fathoms. 12 miles from N.W. Light Ship, 17 fathoms. 10 miles N.W. from Liver- pool Bar Light Ship, 19 fathoms. 2 miles W. from Nelson Buoy. S. Side of Ribble.......<.. Kast Hoyle Bank ......... 15 miles N.N.W. from Liverpool Bar Light Ship, 17 fathoms. Ribble, near Pinfold Buoy, 3 fathoms. 12 miles N.W. from Nelson Buoy, 17 faths. Off Nelson Buoy, 14 faths.. 3 miles W. from Jumbo Buoy. Near Lytham: Pier .22...:. Near No. 5 Buoy in Lune.. 2 miles N.W. from N.W. Buoy, 6 fathoms. Near Jumbo Buoy ....-. 4 miles N.E. from Liver- pool Bar Light Ship, 9 fathoms. Off Nelson Buoy, 9 faths.. 7 miles N. from N.W. Light Ship, 15 fathoms 27/7/07 24/7/07 13/9/07 8/9/07 2/8/07 20/11/07 13/8/07 30/8/07 15/8/07 13/7/07 6/8/07 24/10/07 20/7/07 25/8/07 10/7/07 9/11/07 20/11/07 5/8/07 4/12/07 11/8/07 2/8/07 30/11/07 16/11/07 29/11/07 24/10/07 26/8/07 14/10/07 28/9/07 6/11/07 ee — > =n) 1T 2T 1T 1T 2T SN SN 1T 2T 1T $| IT 2T 2T 2T 2T 2T 1T 27 1T 180 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. We see that 147 plaice were lberated in this experiment and that 36, or about 24} per cent. have been recaught up to the present time. In the corresponding experiments of last year on this station 90 plaice in all were liberated, and if we consider the recaptures of this year we find that 42 of these fishes have now been accounted for, that is 464 per cent., so we may expect that a number of the fishes liberated in July, 1907, will yet be recaptured. As in former years, most of the fishes liberated near Nelson Buoy in the summer months are recaptured on the fishing grounds to the S. and W., only six fishes have been taken close inshore, and there is a rough indication of a migration to the South and West during the summer and autumn months. It is well known that there is a very intense plaice fishery on the fishery grounds lying roughly between the Liverpool N.W. Light Ship and the Morecambe Bay Light Ship during the months July to October, that is, plaice are very abundant here during the period in question. Now we may ask, where do these fishes come from? and only an imperfect answer to this question is afforded by the results of mark- ing experiments. But if we refer to Plate I, representing the results of Experiment 1, 1907, it will be seen that a number of the fishes set free in the Menai Straits in February, 1907, have been recaught on the fishing erounds to the W. and S. from Nelson Buoy. I have no doubt that the majority of the fish caught here have migrated out from the shallow water grounds in the bays and estuaries during the spring months, and that the migration is a feeding one, since one finds that the plaice caught there during the summer and autumn fishery always have their stomachs full of food. The results of Experiment 2 of 1906 also lead to the same conclusion, for we find (see Plate I) that some of the fishes caught in the a SEA-FISHERIES LABORATORY. 16) Lune and Wyre and liberated in February near the place of capture were recaptured during the summer months on the grounds W. from Nelson Buoy. Convincing proof of this offshore migration from the shallow water rearing grounds in the Morecambe Bay area, or in Liverpool Bay, could, of course, be obtained by marking a reasonably large number of fish caught close inshore, but such an experiment would not be easy to carry out unless the fish could be obtained otherwise than by trawling. Hxperiment 4, 24th October, 1907. Station: In Beaumaris Bay, just outside a line from Puffin Island to Great Ormes Head. Fish caught in Menai Straits and in Beaumaris Bay. ANALYSIS OF S1zEs OF FisHEsS LIBERATED. maze (inches). <.......... 8 | 81 84 82 9) OF 94; 93 10 | LOL eer Gt plaice, .6<2... 2-50: op oee ie Ala Spiele | TO 16 (78 Size Gniches) 1 .2..2.. +6 103 101 11 | 114; 114) 113; 12 | 124} 123} — Meroe plaice. , ;...6.0.<00 Sage Goes eon) Pee oi 202: PARTICULARS OF FIsHES RETURNED. | | As 7 3 4 | aS) 61. 7178 LL631 IL | Mostyn ‘Deep; Dee ...4..2-. 22/11/07; 1 | 104 0 oT LL634 9 Conway Bay, 6 fathoms.../ 30/10/07, 0| 9); OJ; IT LL639 103 Red Wharf Bay, 7 faths...| 25/11/07, 1 | 104) 0 | 1T LL644 11 | Conway Bay, 6 fathoms... 28/10/07; 0 | 114) 423) 2T LL650 | 94 Near Puffin Island, 8 | 30/11/07) 1 — | 1T | fathoms. LL852 | 114 | — — —| 124 32 LL855 12 | Red Wharf Bay, 6 faths...) 24/11/07] 1] 12] 0 | 1T LL861 | 104 Between Point Lynus | 18/11/07; 1 | — | — | 1T | | and Great Ormes Head, 10 fathoms. | 132 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. LL862 10 Red Wharf Bay, 10 faths.. | 3/12/07 —j;,—/IT LL863 10 Between Point Lynus and | 14/11/07 103; 3 1T Great Ormes Head, 15 fathoms. LL864 9} Between Point Lynus and | 18/11/07) 1 | 92 4} IT Puffin Island, 9 faths. LL874 92 Conway Bay, 4 fathoms... | 28/10/07} 0 | 10 1) 2T LL871 103 Red Wharf Bay, off | 12/12/07| 21 10% 4) IT Moelfre, 5 fathoms...... LL884 103 Red Wharf Bay, 10 faths.| 3/12/07; 2 | 103; 0 | 1T LL886 94 Red Wharf Bay, 8 faths. | 12/12/07} 2] 9g) 3) 1T LL887 10 Between Point Lynusand | 12/11/07; 1} 10] Oj 1T Great Ormes Head, 15 fathoms. LL888 9 Between Point Lynusand | 14/11/07; 1] 94) 4 1T Great Ormes Head, 15 fathoms. LL892 10 Red Wharf Bay, 7 faths... | 25/11/07|*> 1°) "10% 305s LL893 9 Red Wharf Bay, 10-12) 4/12/07| 2] 94 4 IT fathoms. LL894 9 Conway Bay gaaseeeseeene 31/10/07; O | — | — | IT LL899 84 Red Wharf Bay, 11 faths.. | 12/12/07} 2 | 88) 4 1T LL900 81 Between Point Lynusand | 19/11/07; 1 | — | —| If Great Ormes Head, 9 fathoms. LL901 8 Off Great Ormes Head, 21/11/07; 1)| 8 4 1T 24 fathoms. LL902 84 Red Wharf Bay, off Buoy, | 12/12/07} 2 | 84) 0} IT 10 foot Bank. LL908 92 Off Red Wharf Bay, 10 | 3/12/07 | 2] 10 }| 1T fathoms. LL913 11 Red Wharf Bay, 10-12 | 2/12/07-| 2} 11) O07 UE fathoms. LLSi4 104 Off Great Ormes Head, | 7/12/07 | 2 | 103} 4] 1T 20 fathoms. LL921 10 Off Ormes Head, 20 5/12/07 | 21°10 4) IT fathoms. LL930 10 Conway Bay, 5 fathoms... | 22/11/07} 1] 10] 0O| 2T LL931 103 Off Puffin Island, 10 | 5/12/07 | 2 | 103) 4 1T fathoms. LL933 92 Red Wharf Bay, 10-12 | 3/12/07 | 2 | 103) 3/ 1T fathoms. LL936 93 Mostyn Deep, Dee.......... 23/11/07) 1 93} O| 2T LL938 10 Red Wharf Bay, 10 faths.. ; 8/12/06 | 2) 10] 0, 1T LL940 9 Off Red Wharf Bay, 10 -|.3/12/07 |—2.)|) Sa e0uene fathoms. LL942 9 Red Wharf Bay, 12 faths.. | 3/12/07 | 2] 98 3 1T LL943 10 Near Puffin Island, 9 | 1/12/07 | 2 | 104; 4 1T fathoms. LL950 9} Wild Roads, off Green- | 13/12/07; 2 | 94} 0 | 2T field, Dee. Experiment 4 was made about the end of October, just before the beginning of the plaice fishery, which usually sets in in the autumn and early winter in Red Wharf Bay SEA-FISHERIES LABORATORY. kao and in Channel Course. One hundred and twenty plaice were marked and liberated, and up to the time of writing 37 of these have been returned to me—that is, in less than two months nearly 31 per cent. of these fishes have been recaught. The results of this experiment are represented in Plate II, and it will be seen that, with a few exceptions, all the fishes returned have been caught in the immediate neighbourhood of the place of liberation. Three plaice have migrated off shore, and three have travelled along the coast, and have been recaught in the Dee. The large red spots on the Chart represent the recapture of fish hberated in Red Wharf Bay in September, 1906, but of these five were recaught at the end of that year and the beginning of 1907, and only one plaice caught in the present season’s fishing belongs to last year’s lot. We may conclude then that the stock of plaice appearing in the autumn in the Red Wharf Bay area of each year represents a new stock, and it is very probable that there are plaice which have migrated out from the shallow waters along the North Wales coast and from Menai Straits, since there are no indications from these marking experiments of a migration into this area from the shallow water nurseries on the Lancashire coast. The results of this experiment indicate a great intensity of fishing on the coast of North Wales during the autumn and early winter. We know that this is the case apart altogether from the results of the marking experti- ments, and it appears from the returns of fish landed at Bangor that the present autumn and winter (1907) has been quite exceptional with regard to the amount of fish- ing in Red Wharf Bay and Channel Course. One would naturally conclude from the fact that over 30 per cent. of the plaice marked and liberated have been recaught within two months that the fishing had been very intense ; 134 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. or it may be said that the percentage of these plaice recaught depends entirely on the amount of fishing being carried on in the neighbourhood of the place of liberation. But it is obvious that these two statements mean exacily the same thing, INFLUENCE OF DIFFERENT MertTuops or FISHING. Most of the marked fishes returned during 1907 were caught by Ist and 2nd class sailing trawlers. The following list is compiled from the tables of particulars of fishes returned : — Caught by Ist class sailing trawlers ... see 78 Do. 2nd class do. e a 36 Do. steam trawlers ae M uy 10 Do. trammels, stake nets, “‘ draw nets,” &. 15 Information not given, or doubtful ... he 10 Rate oF Growru or MarkEep PLAICE. Only the results of Experiment 1 in 1907 can be utilised to deduce the variation in the rate of growth from month to month throughout the year. The numbers of fishes returned during the separate months were, however, small, and it does not appear useful to tabulate them here. I have examined the numbers, and the results are very much the same as those given in the last annual report, except that the increase in growth during the summer months does not appear to have been as rapid as is repre- sented in the curve given in the last annual report. The numbers of fishes returned are, however, too small to justify any general conclusions as to a difference in the rate of growth between then and former years. | PLATE L EXPERIMENT I (Black) EXPERIMENT II 1906 (Reqd) Large circles indicate the 40’ aeons wel rhe Fishes \\ Z-2 Liverpool Hoylake, 3 Z Za LZ ea J.J.del. Patel 2“ 50 Z > Luce Bay Z EXPERIMENT I (Black) D EXPERIMENT II 1906.(Red) ZG Large circles indicate the 40) Zz, positions where the fishes ’ Ze are liberated @_Near Corsewall Point. 4-07 SS . | Small circles indicate the @ Near Dundalk .{|-06 'Z positions of recaprure Asn Ha The enclosed numbers are Zz | the months of recapture. 30 Zz | ZW ZZ, < Z Zi 20 667 10° 780 © Morecambe x Bay OF NS é A 54° 906/ 5Oy2 Os a Zip: oC, FEFleetwood WS ee Zz 1 | 4 3557 766 — ge ff Z tht Oo 4 fo. Zit Ge Blackpool 50 558 7 YA g Z 75 Y o ‘@StAnnesZ tipo Gy 777, “4 Z LZ % LD LFV 2 oe y af . pb» 40 1" 596 Sa yy, A ©) Ti al 754 Near Salrees Lightship. ep 30 762 6 ea arg _ Of North Bay Wexford. 554 59: SSI © Off Dinas Head ad ~ ‘ ae i VW i, Mi Plate ll Z / 50 | EXPERIMENT III @teck) | EXPERIMENT IV (Red) Baree circles indicare The +40 posirions where the fishes si Formby Pr. a 30 ® ZZ : ZZ ZZ a Ze Liverpool : 2 ay. Zy, LEA AX Zs ZO Lig CAA ap > oS SA ZS La © : LZ Zina By Zz, 10 Prate Il EXPERIMENT III @ieck) EXPERIMENT IW.(Red) Large circles indicate the positions where the fishes are liberated Small circles indicate the positions of recaprure The enclosed numbers are the months of recaprure iee@ 7. OFF Coningbeg Light; 12% i90@ 1. Not known. -Jixg@3. Mine Head. Irish Coast; 12%" ox@e. OFF Caldy Island; 12%." 2097 do do .1I%" 261@4 OFF Kinsale Head; 104" @\0 OFF St. Patrick’s Island. SEA-FISHERIES LABORATORY. 135 EXPLANATION OF THE CHARTS. Plate I. ’ Represents the results of Experiment 2, 1906, and Experiment 1, 1907. The small red circles indicate the approximate places of recapture of the plaice returned during 1906; the filled-in red circles indicate the positions of recapture of the plaice liberated in this experiment and recaptured during 1907. The numbers within the circles, or outside them in the cases of the 1907 recaptures, indicate the months in which the fishes were recaught. The straight lines do not indicate migration paths, but relate the fish recaptured to their positions of hberation. Plate LI. Represents the results of Hxperiments 3 and 4, 1907. The open black circles relate to the plaice liberated off Nelson Buoy in July, 1907. The filled-in black circles indicate the approximate positions of recapture of plaice liberated near Nelson Buoy in 1906 and recaptured in 1907. The open red circles indicate the positions of recapture of the plaice liberated in Beaumaris Bay in October, 1907. The filled-in red circles indicate the recaptures of plaice liberated in Red Wharf Bay in September, 1906, and recaught either at the end of last year or during 1907. In both charts the numbers outside the circles are the numbers of the labels. To avoid confusion, however, these have been omitted in the case of Experiment 4. rsa J 136 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. RE-DESCRIPTION OF A TREMATODE PARASITE, ALLOCREADIUM LABRACIS (Dusarpin), FROM THE BASS. (Plate III.) By Jas. JOHNSTONE. Bass or Sea-Perch (Labrax (or Centropomus) lupus) in the Irish Sea are nearly always infested with a Trema- tode parasite which is evidently the species Allocreadium labracis (Dujardin). This worm, if not of universal occurrence in the fish, is very common, and I have found it in specimens taken in Cardigan Bay, in the Irish Sea, and in Morecambe Bay. The bass is an inhabitant of the Mediterranean and the adjacent Atlantic coastal waters, where it is very abundant. It enters St. George’s Channel and the Irish Sea in shoals in the early summer, and in June has reached Morecambe Bay, where there is nearly always a fishery for it during June, July and August. About September or October the shoals disappear. The fish appears to be largely a fish-eater, feeding upon young sand-eels and sprats which are abundant in Morecambe Bay during these months. Although common in the English Channel and the Irish Sea area, the shoals do not migrate much further north, and only isolated specimens are taken on the Hast Coast of Scotland, north of the Forth, and in Scandinavian waters. The parasite Allocreadium labracis appears to be a good example of a Trematode which has only one final host, as all the descriptions in the literature appear to relate to worms taken from the intestine of the bass. Thus Dujardin’s original descrip- tion of the species was based on a specimen taken from Labrax lupus, and Stossich and Molin described it from the same host.* In such cases as this the occurrence of a * The literature is summarised by Odhner in Zool. Jahrb. Abth. System., Bd. 14, 1900-1. I am indebted to Mr. W. Nicol, of the Gatty Marine Laboratory, for directing my attention to this paper, and for other assistance. SEA-FISHERIES LABORATORY. 137 parasite is often a useful indication of the places of origin of fishes with periodic migratory habits. The following description of the trematode may be useful, since the species is not at all fully described in the literature. It is based on a reconstruction from a com- plete series of sections made from a worm of 9°77 mm. in total length, the largest found. The trematode was killed by immersion in fresh water, and was subsequently pre- served in formalin, a procedure which enables one to preserve the worm with the minimum amount of dis- tortion. But such a method is not favourable for the study of histological details, and I deal here only with the coarser anatomy of the parasite. The measurements of the specimen are : — Total length: 9°7 mm. Greatest breadth: 2 mm. Transverse diameter of oral sucker: 0°76 mm. a ~ ventral sucker: 0°94 mm. Diameters of ova: 0:079—0:095 by 0:048— 0°064 mm. Transverse diameter of oral sucker is contained 12 times in total body length. Transverse diameter of ventral sucker is con- tained 95 times in total body length. Odhner’s measurements vary slightly from those given above. Thus in his fig. 11, Taf. 33 (op. cit.) the body length is 104 times the transverse diameter of the oral sucker, and 64 times the transverse diameter of the ventral sucker. These ratios are not of precise diagnostic value; thus in a smaller specimen examined I found that the diameter of the oral sucker was contained about 10 times in the body length, and that of the ventral sucker about 7 times. Neither are the diameters of the ova very tonstant. Odhner gives these as 0°07—0°08 by 0-037. 188 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The body is nearly cylindrical, and is only flattened dorso-ventrally at about the middle of the length. It is, asa rule, nearly uniform in diameter only tapering gently at either extremity. The skin possesses no spines or other form of armature. Fig. 1. Allocreadiwm labracis (Duj.). Median longitudinal section through mouth and pharynx. The mouth is subterminal, as is indicated in fig. 1, which represents part of a median longitudinal section. Immediately following the oral sucker, and connected to it by a delicate tube is a strongly muscular, nearly globular pharynx of the usual type. The lumen of the pharynx is a longitudinal dorso-ventral sht, the inner surfaces of which are hard and fibrous. The pharynx passes immediately into a rather short oesophagus which, almost at once, bifurcates to form the two intestinal rami. The two branches of the intestine run roughly parallel to each other to almost the posterior extremity of the body. They have a nearly uniform diameter throughout. The lumen is not a simple one throughout. Round the peri- phery the wall is produced axially into the lumen as a loose vacuolated tissue, the central vacuoles being larger and continuous with each other, and this is the case as far back as the middle of the body. From thence back- wards the vacuolated tissue in the intestine becomes SEA-FISHERIES LABORATORY. 139 looser and finally disappears. The intestine is then a simple, thin-walled tube. There is a very distinct intestinal musculature From the posterior wall of the pharynx a series of strong muscle bundles take origin and pass backwards slightly obliquely to be inserted into the walls of the oesonhagus just behind the pharynx. From here to the extremity of the intestinal branches these longitudinal muscles persist. They always appear in transverse sections of the body as little protuberances on the external surface of the intestine. They do not, however, form very long bundles, but are attached at intervals to the surface of the gut forming a series of short loops. They run quite longitu- dinally, and not at all obliquely. It is these longitudinal muscles which produce the peristaltic movements of the intestine. Circula: muscle fibres are not to be seen in section, and are probably absent. But here and there the gut is attached to the lateral walls of the body by fibrous bundles, many of which appear to be muscular, and the contractions of these extrinsic intestinal muscles are pro- bably antagonistic td those of the intrinsic longitudinal system. The ventral sucker is situated rather nearer to the anterior, than to the posterior extremity. It is not quite round in shape; the longitudinal diameter is the larger in my specimens. The shape of the opening is, of course, variable, but is usually triangular. This sucker possesses a strong extrinsic-musculature. All round its ventral periphery strong bundles of muscular and connective tissue take origin and run out radially to be inserted into the lateral and ventral body walls. Some run dorso- ventrally and are inserted into the dorsal body walls. These muscles, originating in the periphery of the ventral sucker, appear to constitute the principal system. of 140 ‘TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. muscles in the body. There are also muscles which run dorso-ventrally, connecting together the dorsal and ventral body walls, and there are probably some longi- tudinally arranged muscles, though these latter are not very evident. When the animal dies the ventral sucker usually forms a prominent projection on the ventral surface, and the extremities are bent dorsally. This is probably due to the relaxation of the system of muscles surrounding the sucker, and to a contraction of longitu- dinal connective tissue fibres in the dorsal body wall. The genital aperture js situated on the ventral surface in the middle hne, and immediately behind the bifurcation of the intestine. It is not very evident in cleared preparations and can be recognised usually by the protruded cirrus. (Fig. 2.) ns ce S cas eS se so ti oS scapay---Cirrus Sac | a : > Fig. 2. Allocreadiwm labracis (Duj.). Part of median longitudinal section through genital cloaca. The Male Organs (Fig. 3). There are two testes, nearly spherical in shape, but with rather irregular outlines, and nearly equal in size. They are situated nearly midway between the ventral sucker and the posterior extremity of the body. They he one behind the other in the middle line. -Vitelline duct -Vas efferens Se: Fig. 3. Allocreadium labracis (Duj.). Diagram of genital ducts. Projection in vertical horizontal plane. This latter structure is a wide tube situated dorsally to the ventral sucker. It is either a straight, or slightly bent vessel, as is shewn in fig. 8, or is thrown into two or three loose coils, as 1s indicated in Plate III, which is a projection in a longitudinal plane of the genital organs, and has been deduced from a series of longitudinal sections. ‘Ihe seminal vesicle is surrounded by a fairly thick fibrous and muscular sheath—the cirrus-sheath. At about the anterior margin of the ventral sucker the seminal vesicle contracts greatly in diameter to form the cirrus. But the cirrus-sheath is still wide, and the space between cirrus and sheath contains the follicles of the prostate gland. ‘The cirrus itself is a narrow, thick- walled tube, and it is quite unarmed. The cirrus-sheath or pouch terminates in the ventral and posterior part of 142 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. the genital cloaca, and in preserved specimens the cirrus usually protrudes from the opening of the former. The Female Organs (PI. III and fig. 3). The ovary is rather small, and is situated on the right side between the ventral sucker and anterior testis. It is trilobate in shape in the published descriptions of the species, but in my specimens there are always three equal- sized, rounded lobes in a horizontal plane, and dorsal to these, and nearly over the anterior lobe, another from which a short, thin duct takes origin. Immediately dorsal to the ovary, and usually obscured by the latter in cleared preparations, is a capacious receptaculum seminis. The little duct leaving the ovary joins the former at its anterior border. There is a projection of the recepta- culum seminis on its dorsal and anterior part, and from this a fairly wide and thick-walled duct—Laurer’s canal —takes origin, runs at first backward and upward forming a prominent bend, and then passes obliquely forward to open on the dorsal surface of the body and nearly in the middle line. Laurer’s canal was empty in my specimens. ‘The receptaculum seminis contained granular matter, the nature of which could not be deter- mined: it was probably broken down spermatozoa. Just where the duct from the ovary joins the receptaculum seminis the ootype takes origin. This is a very narrow tube which runs at first directly forward, through a mass of loose gland follicles, which together form the shell-gland. Emerging from the latter (which, of course, opens into it) the ootype enlarges greatly to form the uterus,and the latter 1s thrown into a series of close convolutions filling up most of the space between ovary and receptaculum seminis behind, and ventral sucker forward. The uterus is not nearly so capacious as in-many other trematodes. Its general appearance and SEA-FISHERIES LABORATORY. 1438 distribution is represented in Pl. III. Im fig. 3 the convolutions are represented diagrammatically to secure clearness. For the same reason the eggs have been omitted in both figures. The uterus passes forward over the ventral sucker, at first side by side, and then dorsal to, the seminal vesicle. It contracts greatly in diameter in the neighbourhood of the latter structure. Here, and here only, the uterus is muscular. Just over the prostate gland there is a sphincter muscle (fig. 2), the contraction of which usually reduces the calibre of the uterus to much less than the diameter of an ovum. In fig. 2 this sphincter is represented as a long-drawn-out structure, but in other sections I have seen it as a short, thick, flat ring of muscle fibres. This indicates that there are pro- bably also longitudinal muscle fibres present, though it is difficult to see these. The structure functions doubtless in the extrusion of the ova. Immediately in front of this sphincter muscle the calibre of the uterus enlarges, and we have a fairly wide chamber which is the genital cloaca (fig. 2). In this, as the figure shows, there are usually a few egos. The opening on the surface of the body is circular. Into the terminal part of the genital cloaca there opens the cirrus pouch, and usually the cirrus itself protrudes from the latter, and out from the genital aperture on to the surface of the body. | The vitellaria are very characteristic. In a cleared _ preparation they appear to ramify over every part of the body, obscuring most of the other organs. ‘This is par- ticularly the case at the posterior extremity, where the vitelline glands appear to fill up the whole body. But in section they are seen to be arranged peripherally, generally as a single stratum of gland follicles. At the middle of the body they are dorsal and lateral]. In front L 144 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. of the ventral sucker they are present only beneath the dorsal body wall. In the region of the testes they are lateral (fig. 4) and do not appear on dorsal and ventral surfaces. Behind the testes they are distributed round the entire periphery of the body. They are very numerous, and when the worm is contracted greatly appear very closely packed together, so that it is almost impossible to make out the other organs. Indeed it is only by killing the trematode in fresh water, and then by flattening it out between two microscope slides during fixation, that the animal can be preserved in a condition fit for staining and clearing. faaria’ Ne stis — Excretory a oles duct Pe betes Wy \ ) se oe Fig. 4. Allocreadiwm labracis (Duj.). Transverse section through posterior testis. The vitelline ducts have the usual disposition. It is not difficult to trace most of their ramifications in a successful preparation. One main longitudinal duct runs along either side of the body, and to this numerous ductules proceed from the follicles of the gland. At about the transverse level of the ovary fairly wide transverse ducts appear, and these run across towards the middle line, uniting to form a rather large vesicle, which is, of course, only an enlargement of the united ducts. From this vesicle a slender efferent duct takes origin, and runs Prats IT. Genital @ aperture € Vitelline duct-- es PON. A: Vesicula- Uterus oN seminalis i 5 |Nentral sucker i \ = = $5t-Receptaculum 7& hs. seminis al fot Lacretory 2 Ge H Allocreadium labracis (Dujardin), Dorsal aspect. Reconstructed from serial sections mag.= x18. SEA-FISHERIES LABORATORY. 145 obliquely forward to pass into the midst of the follicles of the shell gland. It is difficult to trace in section, but can be seen to open into the ootype as the latter passes through the shell-gland. 3 The excretory system cannot be traced in sections. There is one main vessel which opens to the surface at the very posterior tip of the body. It is elongated dorso- ventrally. It can easily be traced in section as far forward as the testes, and here it is lost. Doubtless it breaks up in the characteristic manner into a multitude of smaller vessels, but I could see no indication of the usual two lateral excretory vessels uniting in the region of the oral sucker. But it is always much easier to trace the excretory system in the living worm, and I had no opportunity of examining such specimens. Puate ITT. Allocreadium labracis (Dujardin). Reconstructed from a series of transverse sections. Magnified about 18 diameters. — 146 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. REPORT ON THE HYDROGRAPHIC WORK IN THE KASTERN PORTION OF THE IRISH SEA BETWEEN JULY, 1906, AND NOVEMBER, 1907. By Henry Bassett, Jun., B.Sc., Ph.D., Demonstrator and Assistant Lecturer in Chemistry in the University of Liverpool. The seas surrounding the British Isles are filled with only slightly diluted Atlantic water. Speaking generally, the water filling the Irish Sea is a good deal more dilute than that in the English Channel and the North Sea, and, owing to the tidal current which runs from South to North through the Irish Sea and round the North Coast of Scotland, the water from the Irish Sea plays a very important part inthe dilution of the Atlantic water which goes to fill the North Sea. The Irish Sea is plainly so dilute because of the large volumes of fresh water flowing into it from the land. Now a very large proportion indeed of the fresh water running into the Irish Sea runs into that portion of it which is situated to the Kast of a line drawn from Burrow Head, in Wigtownshire, due South to Anglesey ; for most of the drainage from the parts of England and North Wales having the largest rainfall passes into this portion. This part of the Irish Sea is also remarkable for its strong tides, and these, owing to the peculiar con- formation of the coast line, and the position of the Isle ) of Man, cause a very thorough mixing of the waters, and . ensure the efficient dilution of any salter water coming in from the South, SEA-FISHERIES LABORATORY. 147 A study of the salinity of this portion of the Irish Sea promised, therefore, to be of considerable interest. For some years past temperature and salinity measurements at various depths have been made in the Western portion of the Irish Sea by the Irish Board of Agriculture and Technical Instruction, under the direction of Mr. E. W. L. Holt; but up to 1906 the Hastern portion had been left almost entirely alone. From 1904 onwards the “ Bulletins trimestriels du Conseil permanent international pour l’exploration de la mer” give the results of salinity and temperature observations made on surface samples collected by the Bahama Bank (54° 19/ N; 40° 13’ E) and Cardigan Bay (52° 24' N; 5° 00’ E) lightships. From this information surface isohalines are drawn in the published charts. In July, 1906, a systematic study of the Hastern por- tion of the Irish Sea was begun under the scheme of hydrographic observations sanctioned by the Lancashire and Western Sea-Fisheries Committee. On the first voyage samples were collected from points situated on lines drawn from Piel Gas Buoy to Maughold Head, and from the Calf of Man to Holyhead breakwater. A few samples from other positions were also collected on this trip. These two lines were kept to until the end of 1906, during which interval of time two more trips were made. For the next two trips (February and May, 1907) the first line of soundings was altered to one running W.N.W. from Piel Gas Buoy instead of N.W. The other line remained as before. Finally, in July, 1907, the first line underwent a slight alteration so as to make it run along the 54° of latitude and to bring it into agreement with the line of soundings run out from the Irish Coast to the Calf of 148 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Man by Mr. Holt. The Jine from the Calf of Man to Holyhead still remained as before. In May, 1907, the area under investigation was extended somewhat, an additional line of soundings being run across Carnarvon and Cardigan Bays. The water samples, except those from the surface, have always been collected by means of a Nansen- Pettersson water-bottle, while the temperatures have been taken with the usual pattern of thermometer used in the International Fishery Investigations. The titrations of the water samples have been carried out in the usual way by Mohr’s method,* and the salinities, etc. calculated by means of Knudsen’s Hydrographic tables. The titrations have all been done by myself, but I have only occasionally been able to go out on the steamer collecting the samples. The latter have usually been obtained by my colleague, Mr. James Johnstone, whom I have much pleasure in thanking for this and much other assistance. My thanks are also due to Captain A. Wignall, of the “John Fell,” the steamer of the Lancashire and Western Sea-Fisheries Committee, from which all the observations have been made, for the skill with which he has fixed the positions of the soundings. The salinites and other details for the various stations are given in the following tables. ‘he first column gives the depth in metres; T° is the temperature (Centigrade) of the water im setw; Cl °/,, 18 the amount of chlorine per 1000 parts of water as found by the titration; S °/,. is the salinity; and 1 + Ti elves the density of the sample of water at the temperature T°. The position of the station and the date on which the samples were collected are given above each table. *For details of the method as apphed to hydrographic work, see Niels Bjerrum, Meddelelser fra Kommissionen for Havundersogelser. Serie: Hydrografi. Vol. I, No. 3.—Copenhagen, 1904. SEA-FISHERIES July 2 to 5, 1906. The positions on the two chief lines are given first. LABORATORY. 149 0/7/06. 54° 4’ N.; 3° 23’ W. Depth of station, 22 metres. Depth (metres) T Cliiee Soh on 0 14°15 18°18 32°84 24°52 9:2 13°5 18°16 32°81 24°64 18°3 13°5 18°16 32°81 24°64 o/7/06. 54° 7 N.; 3° 37’ W. Depth of station, 50°2 metres. Depth (metres) dn Clas S) igs | Ot 0 15:96 18°14 32°77 24:08 9°2 13°5 18°15 32°79 24°62 18:3 12-2 18°36 33°17 25°14 27°5 Lig 18°39 33°22 25°26 o/(/06- 54° 11’ N.; 3° 51’ W. Depth of station, 27°65 metres. Depth (metres) ) 9°2 18°3 25°6 pe 15°55 12°80 12°30 12°25 C1 loo 18:14 18:29 18-46 18-46 8 °/oo 32°77 33°04 33°39 33°39 Or 24°18 24°95 25°28 25°29 0/7/06. 54° 14’ N.; 4° 3’ W. Depth of station, 27°5 metres. Depth (metres) 0 92 23°8 mo 14°6 12°6 12°3 Cl °/o0 18°44 18°52 18°54 150 ‘TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 3/7/06. metres. Depth (metres) 0 9:2 18:3 36°6 54°9 13°2 3/7/06. metres. Depth (metres) war 03° 90! No; 4°'o6° Mi pe 12°46 12°15 12°15 53° 49’ N.; 4° 46’ W. ie or ww DOOD COIS COM Iieit$) OZ 11:02 11-00 11°00 C1 foo 18°91 18°90 18-90 Geil 18°90. » Bigs 34°16 34°14 34°14 34°16 34°14 Depth of station, 76°9 Depth of station, 53:1 03° 37’ N.; 4° 42’) W. Depth of station, ot+9 3/7/06. metres. Depth (metres) (te Clie 0 11°72 (18°89 9-2 11:00 18°90 18°3 1100) Sas a leise 36°6 1EOOs (a5) ROS :90 54°9 1100) ys eas-90 ao) SEA-FISHERIES LABORATORY. eg 3/(/06. 53°29’ N.5-4°9 40’ W. Depth of station, 64°1 metres. Depth (metres) abe GS) ee / 0O Or 0 11°80 18°85 34-05 25°90 9-2 11°62 18°82 34-00 25°88 18°3 11°60 18°82 34-00 25°88 36°6 11-60 18°83 34-02 25°90 54:9 L155 18°86 34-07 2594. 3/7/06. 538° 24’ N.; 4° 39' W. Depth (metres) le | Cl. Sa ane Ct 0 | 11-65 | 18:87. 34:09 | 25°95 Samples were only collected from the following stations on this one trip. 2/1/06. 53° 26 N.; 4° 26) W. Depth (metres), dhe CN ae ay ee or ti | 12:80 1875 | 3387 25-70 } 3I7/06. 54° 22' N.; 4° 34' W. Depth (metres) Ts (eel cieree See Gi 0) mee! 7c 9) | 18°89 — 34°13 | 25°90 3/1/06. 54°25’ N.; 4°21' W. Depth of station, 23°8 metres. _ Depth (metres) iby Yl ie My) ee om 0 | Webs |. fas7s 33°93 25°68 9-2 | 1200 -|\ 1878 33-93 25°78 18°3 be 12°00 —i7, 18-76 33°89 25°75 152 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIEE3: 3/7/06. 54° 22' N.; 4°19! W. Depth of station, 311 metres. a a a i Depth (metres) Al | CEs. Seine CO; 0 12°95 18:58 33°57 25°31 9-2 12°30 18°56 33°53 25°41 18°3 12°23 18°57 33°5D | 25°44 27°5 E223) ae lisse 33°57 25°45 3/7/06. 54° 22’ N.;.4° 2’ W. Depth of station, 403 metres. Depth (metres) as Cia See om ) 14°] 18°29 33°04 24°69 9:2 12°70 18°31 33°08 24°98 18:3 12°60 18°32 33°10 25°01 36°6 11-35 18°46 33°35 25°45 0/7/06. 54° 0! N.; 3° 13’ W. Depth (metres) oe Cla Spies o; 0 17-00 17°53 31°67 23°00 | Oo, SHO a IN. § GOI! WW Depth (metres) as Clogs S ae or 0 15°90 18:09 32°68 24°01 aii00, 032.08 INGE No aoa | : Depth (metres) aly, Olig/ a. iene ER ema de ats | 0 16:00 17°64 31°87 23°37 SEA-FISITER IES LABORATORY. Be 153 Surface samples collected on July 9 and 10, 1906. Position. He Chie MS) Yee on 5a ON. ; 4° 43’ W. 12:9 18°88 34°11 20°75 bo lOO N. ; 4°43" W. 12:2 18°95 34°23 25°98 53° 1’ N.; 4° 44’ W. 11°4 19-03 34°38 26°25 52°52’ N.; 4° 45’ W. Jelly) 19-02 34°36 26°14 52° 47’ N.; 4° 43’ W. 12-9 18°89 34°13 25°76 52° 26’ N.; 4° 34’ W. 13°8 18°86 34:07 25°61 oa 48’ N.; 4° 27° W: 14°8 18°82 34°00 25°27 52° 13’ N.; 4° 24’ W. 15-0 18°69 33°77 25°04 September 18 and September 19, 1906. 18/9/06. 54° 3’ N.; 3° 22' W. Depth (metres) 7° Cle Sra Gi 0 15°20 18°25 32°97 24°40 9-2 13°50 18°26 32°99 24°77 22°0 13°50 18°24 32°95 24°74 18/9/06. 54° 7.N.; 39 36° W. Depth (metres) i bag (OLS Ae S) Yes OF 0 15-00 18°38 30°21 24°63 9-2 14:00 18°37 33°19 24°83 18°3 14:00 18°51 33°44 25°02 27°5 14:00 18°53 33°48 25°04 PSio00;, 04°40 Neo 30 AW. Depth (metres) — Clee Siig /Pes ot 0 15-2 18°44 33°31 24°67 9:2 14:0 18°46 33°35 24°94 18°3 14:0 18°47 33°37 24°95 27°5 14-0 18°47 33°37 24°95 154 TRANSACTIONS LIVERPOOL BIOLOGICAL 18/9/06. 54°14’ N.; 4° 2) Ww. Depth (metres) ils lng a. S foo shore oh a BaeScet! 0 clint | 18°52 33°46 9°2 | 14:0 18°52 33°46 18°3 | 14:0 18°52 33°46 27°5 14:0 18°52 33°46 19/9/06.: 53° 06 N.; 4°47) W. Depth (metres) T Cleve. 5 eee 0 13°7 18°84 34:04 9°2 13-0 18°85 34:05 18:3 13-0 18°84 34:04 36°6 13-0 18°84 34:04 53-1 13-0 18°84 34:04 19/9/06. 53° 47’ N.; 4° 45’ W. Depth (metres) i Clarice S oo 0 13°7 18°89 34°13 9°2 13°5 18°88 34°11 18°3 13°2 18°88 34:11 36°6 13:2 18°88 3411 58°6 13°2 18°88 34°11 199/065 93° 38 WN ae 4 Ve Depth (metres) dls Clivies Racias 0 13°8 18°89 34°13 18°3 13°5 18°90 34°14 36°6 13°5 18°88 34°11 54:9 13°5 18°89 34°13 69°5 13°2 18°88 3411 SOCLETY. 25°54 25°68 25°67 25°67 25°67 Ot 25°60 25°63 25°69 25°69 25°69 SEA-FISHERIES LABORATORY. 29/9/06. 53° 28’ N.;.4° 40° W: Depth (metres) As CEP) Sans On 0 14:7 18°84 34°04 25°34 9-2 eestoeS 18°82 34°00 25°49 18°3 13°8 18°84 34°04 25°54 36°6 13°5 18°83 34°02 25°57 64:1 13°5 18°83 34°02 25°57 November 13—November 14, 1906. 13/11/06. 54° 3'N.; 3° 22’ W. Depth (metres) A Ce CES SS) ee om 0 | 10) 86 |S 18-49 33°40 25°56 fa 0 | 18 49 | «88-40, 25°56 ; 2577 BED — 1849 33°40 25°56 13/11/06. 54°7' N.; 3°36 W. Depth (metres) ok Clee ss S) es Gi 0 ly pecbbod 18°62 33°64 25°72 9°2 11-3 18°62 33°64 25°68 27°5 11°3 18°65 33°69 25°72 ESTO. 54° LON 43°00) W. Depth (metres) Ae Clie. SS) Iles Gn 0) 1 18°30 33°06 25°27 9°2 10°7 18°28 33°03 25°30 26°D 10°7 18°29 33°04 25°31 156 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 13/11/06. 54° 14’ N.; 49 2/ W. Depth (metres) A ti Chs?/. Sia a; 0 10°6 18°29 33°04 | 25°33 9-2 10°6 18°30 33-06 | 25°34 22°0 10°6 18°25 32°97 25°27 14/11/06. 53° 56’ N.; 4° 47’ W. Depth (metres) is Chie. Ries rok 0 11°3 18°78 33°93 25°90 92 Tolea 18°74 33°86 25°88 27°5 Nhe 18°75 33°87 25°90 45°8 ILI 18°75 33°87 25°90 14/11/06. 53°47’ N.; 4° 40’ W. | Depth (metres) T° Chie. Sif eee | Gi 0 11:8 18°83 34:02 25°89 9°2 11°6 18°84 34°04 25°93 36°6 11°6 18°82 34:00 25°90 64-1 116 18°82 34:00 25°90 | 14/11/06. 58° 38’ N.; 4°43! W. Depth (metres) are Cleo SY fine on ag 0 12-0 18°84 34°04 25°86 9:2 ESS) 18°83 34:02 25°87 45°8 12-0 18°84 34:04 25°86 SEA-FISHERIES LABORATORY. a iy) February 15—February 18, 1907. 13/2/07 (10-40 a.m.) 54° 1'N.; 3° 30' W. Depth (metres) T° GR ae o, 0 3-6 17:88 32°30 25°71 18:3 3-5 17:89 32-32 25-74 27-5 | 35 17:89 32°39 25°74 13/2/07 (11-50 a.m.) 54° 2'N.; 8° 47 W. Depth (metres) fe i, CL. Ses | or 0 Wage 2 25-20 39-99 26-08 18°3 34 | “18:91 39-90 26°19 36-6 35- | 18-99 39-99 26°19 13/2/07 (1-0 p.m.) 5492’ N.; 4°4/ W. Depth (metres) pee Clie See | Gr 0 59 18°40 33°24 26°22 18°3 5:3 18°37 33°19 26°23 27°5 5:3 18°38 33°21 26°24 cl?) a3, a Depth (metres); dN ih 0 5°65 18°54 33°49 26°44 18°3 D°6 18°54 33°49 | 26°44 34°8 56 18°53 33°48 | 26°43 18/2/07 (1-0 p.m.) 53°53) N.; 4° 46’ W. Depth (metres) deg Clee. Si ie on 0 13 19-04 34°40 26°93 18°3 6°9 19°03 34°38 26°97 36°6 6°9 MEO! 34°38 26°97 D4°9 6°9 EO ss 34°38 26°37 158 TRANSACTIONS LIVERPOOL | Depth (metres) 0 18°3 36°6 D4°9 Te 18/2/07 (10-40 a.m.) Depth (metres) 0 18°3 36°6 54:9 May 6—May 8, 1907. 6/5/07 (8-50 a.m.) P| 6-7 6°5 6°5 6°5 | 1] O, Ces 19-00 18°98 18°99 hous) C1" foo 18°68 18°69 18°69 18°72 station, 28 metres. Depth (metres) a NC CH OO bd SS = 6/5/07 (10 a.m.) station, 40°3 metres. Depth (metres) BIOLOGICAL 33°75 18/2/07 (11-55 a.m.) 53° 43) N.; 4° 44’ W, me) ») ‘00 34°33 34°29 34°31] 34°31 53° 33’ N.; 49 41 W, 33°77 33°77 33°82 p40 1 NU; oo al ae Ono 18-02 18°03 18:07 18°19 0; S /oc 32°56 32°65 | 32°86 | bdo Ot IN, 2 SON Al SOCIETY. Depth of OC; 25°39 25°43 25°49 25°66 Depth of SEA-FISHERIES LABORATORY. 159 Osi0e Gill tacms) eyo? 20 N.; 424° W.) Depth. ot station, 38°5 metres. Depth (metres) Age Ces Sian Or 0 84 18°63 33°66 26°18 9-2 7:75 18°64 33°68 26°30 18°3 78 18°63 * 33°66 26°28 36°6 ce 18°68 33°75 26°36 6/5/07 (noon). 54° 3’ N.; 4° 20'W. Depth of station, 42°] metres. i , Depth (metres) f° Oli Se Or 0 81 18-96 34°25 26°69 92 7°85 18:97 34°27 26°75 18°3 7°85 18:97 34°27 26°75 36°6 78 18°96 34°25 26°73 7/5/07 (8-40 a.m.) 53° 53’ N.; 4° 46° W. Depth of station, 64°1 metres. Depth (metres) i? Cle -. Seas on 0 (ie) 19°00 34°33 26:79 9°2 75 19-02 34°36 26°87 18°3 76 19-04 34°40 26°90 36°6 76 19-05 34°42 26°91 60°4 76 19-05 34°42 26°91 7/9/07 (10 a.m.) 53° 43’ N.; 49 44’ W. = Depth of station, 64°1 metres. Depth (metres) flog Chai Ser. oan 0 795 18-98 34°29 26°74 9-2 T75 18°97 34°27 26°78 18°3 775 18:99 34°31 26°81 36°6 (at! 18-98 34°29 26°79 60°4 TT 19-00 34°33 26°82 “a 160 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 7/5/07 (11-25 a.m.) 53° 33'N.; 4° 41’ W. Depth of station, 58°6 metres. | Depth (metres) ‘Dag OLE) et] See or 0 81 18°80 | 33°96 26°45 9°2 8:0 1878 | 33°93 26°46 18°3 8-0 18°78 33°93 26°46 36°6 8:0 T3210 33°95 26°48 54°9 80 18°79 33°95 26°48 T/oj07 (2-25 p.m.) 038° 8!N.; 4° 44° Wl Depthmas station, 58°6 metres. Depth (metres) Ee Clie. Sao or 0 83 18°95 34°23 26°65 eZ 8:1 18°95 34°23 26°69 18°3 7:95 18°96 34°25 26°71 36°6 Py 18°94 34°22 26°69 D4°9 1 18°94 34°22 26°69 8/5/07 (9-15 a.m.) station, 43°9 metres. b2° 34’ N.; 4° 45’ W. Depth of Depth (metres) a Ol es S248 on 0 8:7 18°84 34°04 26°44 9:2 8:4 18°84 34°04 26°49 18°3 8-4 18°84 34°04 26°49 | 36°6 8:4 18°84 34°04 26°49 8/5/07 (10-30 a.m.) 52° 24'N.; 4° 43’ W. Depth of station, 40°3 metres. 4 Ne Ot Depth (metres) Os S 5/48 0 8°8 18°81 33°98 26°38 9°2 8°7 18°81 33°98 26°39 18°3 8°65 18°81 33°98 26°39 36°6 86 18°81 33°98 26°40 SEA-FISHERIES LABORATORY. 161 July 29—July 30, 1907. 29/7/07 (8-380 a.m.) 954° N.; 3° 30' W. Depth of station, 27°5 metres. Depth (metres) ils Clea SP ee Gi 0 15°8 17°64 31°87 23°42 9-2 13°5 17°76 32°09 24:07 18°3 13-0 18-11 32°72 24°66 27°5 13-0 18:13 32°75 24°69 29/7/07 (9-50 a.m.) 54° N.; 3° 47° W. Depth of station, 36°6 metres. Depth (metres) re Che foc Speen Or 0 13-0 18°67 33°73 26°43 9°2 12°8 ebyial 33°80 26°54: 18°3 12°8 18°72 33°82 26°56 36°6 12°8 eal 33°80 26°54 2o/(/07_ C11-10 a.m.) 54° N.; 4°4' W: Depth of station, 36°6 metres. Depth (metres) TS Olay Ses Oo 0) 13-0 18°85 34:05 .| 26°68 9-2 12°5 18°85 34:05 26°78 18°3 12°5 18°85 34:05 26°78 36°6 12°6 18°85 34:05 26°76 29/7/07 (12-30 p.m.) 54° N.; 4° 20' W. Depth of station, 45°8 metres. Depth (metres) ie Clee aa Sy Be or 0 | 19-6 18°88 34-1] 25-81 18°3 ee 18:88 34-1] 25°87 36-6 | 193 18°87 34-09 25°85 45°8 12°3 18:87 34-09 25-85 162 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 29/7/07 (3 p.m.) 53° 53’ N.; 4° 46’ W. Depth of station, 73°2 metres. Depth (metres) a, Chrys. Sie mr 0 12°3 18°89 34°13 25°88 18°3 12°1 18°88 34°11 25°90 36°6 12:0 18°88 34°11 25°92 64:1 Wis) 18°87 34°09 25°92 29/7/07 (4-25 p.m.) 53° 43’ N.; 4° 44’ W. Depth of station, 04°9 metres. Depth (metres) ie Ol S ies Or 0 12-1 18°87 34°09 25°88 18°3 LL) 18°87 34°09 25°92 36°6 11:9 18°87 34°09 25°92 53°1 the) 18°87 34°09 25°92 29/7/07 (5-45 p.m.) 53° 33'N.; 4°41! W. Depth of station, 54:9 metres. Depth (metres) ibs Clie. oma = oy 0 12°9 18°81 33°98 25°66 18°3 12°7 18°80 33°96 25°68 36°6 12°7 18°80 33°96 25°68 53:1 12°7 18°80 33°96 25°68 29/7/07 (8-45 p.m.) 63° 5’ N.; 49 44° W. Depth of station, 64:°1 metres. Depth (metres) ‘ls Clic Sai or 0 13°25 18°84 34°04 25°63 18°3 12°8 18°86 34:07 25°75 36°6 12°5 18°87 34:09 25°82 30/7/07 (8 a.m.) SEA-FISHERIES station, 36°6 metres. — 0 9-2 18°3 36°6 Depth (metres) ape bY 11°8 11°6 £6 Cl "fcc 18°85 18°85 18°86 18°85 LABORATORY. 62° 34’ N.; 4° 40’ W. 8 */oo 34:05 34°05 34:07 34:05 163 Depth of Ot 25°90 25°92 25°98 25°96 30/7/07 (9-25 a.m.) 52° 24'N.; 4° 43’ W. Depth of station, 36°6 metres. Depth (metres) ‘lhe Cl S) glee Ot 0 14-0 18°78 30°93 25°38 9-2 13°25 ieee 33°91 25°53 18°3 13°25 18°78 33°93 25°54 36°6 13°25 18°78 33°93 25°54 November 4—November 6, 1907. 4/11/07 (11-5 a.m.) 54° N.; 3° 30'W. Depth of station, 29°3 metres. Depth (metres) a Clie. SS glee om 0 Prd 18°32 33°10 25°23 9°2 11°55 18°37 33°19 25°31 18°3 1ST! 18°44 33°31 25°38 27-5 WEY: 18°45 33°39 25°39 | 4/IVj07 (12-lo p.m.) , 04° N.; 3° 47 W. Depth of station, 39°8 metres. Depth (metres) le Che Sy ie on 0 11:9 18°62 33°64 25°58 57 11°8 18°63 33°66 25°61 18°3 11°8 18°63 30°66 25°61 36°6 Lis 18°63 33°66 25°61 164 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 4/11/07 (1-24 p.m.) station, 42:1 metres. 54° N.; 4° 4’ W. Depth of Depth (metres) ane C1 Fis. Sie or 0 118 18°75 33-87 25°78 9:2 Piers) 18°74 33°86 25°77 18°3 1:7 18°75 aa o's 25°80 36°6 11°8 18°75 BDIOL 25°78 4/11/07 (2-30 p.m.) 54°N.; 4° 20' W. Depth of station, 46°7 metres. Depth (metres) ie Chee. 2, See or 0 11°8 18°76 33°89 25°79 9°2 11°75 18°75 33°87 25°78 18°3 11°75 18°75 33°87 25°78 40°3 11-75 18°75 33°87 25°78 6/11/07 (10 a.m.) station, 87°8 metres. Depth (metres) 0 18°3 36°6 549 82°4 53° 53’ N.; 4° 46’ W. Depth of 5/11/07 (11-25 a.m.) of station, 64°1 metres. Depth (metres) 0 18°3 36°6 54:9 i Cl rps S tien 12°45 18-82 34-00 12°6 18-82 34-00 12-4 18-80 33-96 12-4 18-80 33-96 124 18°82 34-00 53° 43' N.; ie Cl ee S Wee 1257 18-79 33-95 ry 18-79 33-95 12°6 18-79 33-95 12°6 18°78 33:93 4° 44’ W. SEA-FISHERIES 5/11/07 (12-35 p.m.) of station, 64°1 metres. LABORATORY. 165 93° 33’ N.; 49° 41’ W. Depth Depth (metres) Ee 0 12°4 18°3 23 36°6 12°4 54-9 12-4 6/11/07 (11-30 a.m.) of station, 64:1 metres. Depth (metres) di 0 12°6 18°3 12°5 36°6 12°5 50°3 12°5 6/11/07 (2-30 p.m.) station, 36°6 metres. Depth (metres) du 0 12°35 9°2 235 18°3 12°35 36°6 12-4 6/11/07 (3-50 p.m.) station, 36°6 metres. Depth (metres) 0 9°2 18°3 34°8 re PA 12°15 12°3 12-2 Cl Ser Ss wise Ot 18°67 ate 25°55 18°67 30°73 25°57 18°67 30°73 25°55 18°67 30°13 29°55 53° 5’ N.; 4° 44’ W. Depth Cl Pies S ies Oe ROANG 34°61 26°21 19-15 34°60 26°21 19°15 34°60 26°21 19°15 34°60 26°21 02° 34' N.; 49 45’ W. Depth of Cl Bie S Aes Cit 18°98 34°29 26°00 18°95 34°23 25°96 18°96 34°25 25°97 18°96 34°25 25°97 O2° 24’ N.; 4° 43’ W. Depth of Oe 18°84 18°82 18°84 18°85 Si / ee 34:04 34:00 34°04 34°05 Ot 25°85 20°81 25°81 20°84 166 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. A careful consideration of the above tables will show that :— (1) In the majority of cases the water at any given spot has practically the same salinity from top to bottom. There are, however, some well-marked exceptions to this, the stations affected being in the shallower water north of the 54 parallel of latitude. In these exceptional cases there is a more or less rapid increase in salinity with depth. The probable explanation of this will be discussed presently. (2) There is a small but unmistakeable seasonal variation in the salinities. To bring out this second point more clearly the salinities at the chief stations for the various months have been collected in the following table. In most cases the salinities have been given to the first place of decimals, and in the case of those stations in which the water at the surface differed markedly in salinity from that at the bottom both top and bottom salinities have been given. For the present purpose those positions which are bracketed may be considered as one station. In so far as one is justified in drawing conclusions from only a year and a-half’s work, it would appear that at the first four stations the salinity is at a minimum somewhere about February. The maximum salinity is not so well marked but seems to occur between July and November. In the case of stations 5 and 6 exactly the reverse holds, the maximum salinity occurring in February and the minimum in November. Station 7 which, like 5 and 6, is on the line Holyhead—Calf of Man, resembles stations 1-4 from the fact that the minimum salinity occurs about February. This difference in the time of minimum salinity is SEA-FISHERIES LABORATORY. 167 Position July | Sept. | Nov. |. Feb. | May | July | Nov. 1906 | 1906 | 1906 | 1907 | 1907 | 1907. 1907 ee en ie WG eS Nieicey een me 3 W- [32°75 (33-3 ees! Woorl| — () —. | — - | 308 eaee Mae fa 54° 3’ N. ; 3° 29/ W. RORY A ee C mae, OM pees aM, eal pene 71 2 . 20 4nv _ fon ia ae (33°73 33°64 eet! WW. | i. (33-80 heen MeyN.: 3°47 w. /2| — | —. | — | 3299 eae 2 bdo 7’ N. ; 3°36’ W. | eae teem dee ea ee BAO N.; 4° 4’ W. —- ss = = cos 34:05 | 33:9 Meee ae sa | | { . ° pa? 10’ N.; 3°50'W.} |y559 Seng 00 pe eae 54° N. : 4° 20’ W. — — es deat = 34°] 33-9 ree | = Pe | 935) es | 54° 14’ N.; 4°! W. nee PGR eas nes is 2 mete, >a Memeo. y | = | — | aaa (878 | 34-1 | 360 meen 47 wW.)° | 342 | 340 | ss9 | — | — |-— | — eee wey) | | — «=| es | Bes | 24d | 33gb mee AT’ N.; 4°45’ W.) | 34:15 | 34:1 | 34:0 a ee 2s = Mee 4 W)| — | — -| — | 398 | 3305, | 360 | 33% meen 4°43 wf! | 341. | 3417,1 340 | — | — | — | = 3° 5 N.: 4°44’ W. sy | a EE Rees eve a) ov 52° 34’ N.; 4° 45 W. se ag eves || eyes 52° 24’ N.; 4° 43’ W. ee eT ee © 2133-98 33-0) |) geo 168 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. probably due to the way in which the mixing of the fresher and salter water is brought about by the tides, which cause the salter water at stations 5 and 6 to be gradually diluted by the less salt water from further north. This will obviously result in the minimum salinity at stations 5 and 6 roughly corresponding with maximum salinity at the more northerly stations. The different behaviour at station 7 is no doubt due to the fact that at that point the tide running north is much stronger than that running south, so that there is a continuous shght stream from the south. These last considerations make it clear that in considering the seasonal variation of salinity, the effect of the tides must be borne in mind. As already mentioned, the portion of the Irish Sea with which the present investigations deal is noted for its strong tides, so it seemed hkely that the salinity at any given spot would depend to a slight extent on the state of the tide: as this changed, so the water originally present would be replaced by other water which might well differ in salinity. It was important to see whether any differences so caused were appreciable and hkely to mask any seasonal change in the salinity. Samples were accordingly collected from one of the stations every two hours throughout a tidal cycle. The station chosen was that at 54° 2’ N.; 3° 47’ W., as being one at which any such effect would probably be well marked owing to the proximity of the large body of water of low salinity in Morecambe Bay. The results obtained are given in the following table: SEA-FISHERIES LABORATORY. 169 July 2,1907. 54° 2'N.; 3°47’ W. (Sea smooth and weather fine all day.) Depth Te esl Ch Mee Sie plier 0 eG 18:57 33°55 MPN) | \ Geo Oem, 2 lay 9°2 Ta 18°56 33°53 25°56 20 min. after 44:7 J tieah 18°62 33°64 2:61 High Water. (bottom) | 0 12:0 18°60 33°60 MSS) Pee) aaa, 2 44), 9:2 ed 18°57 33°55 25°58 20 min. after 40°3 11:4 18°63 33°66 25°68 High Water. (bottom) 7 0 al 18:57 33°55 2D Ai, | 10.30 a.m. ; 9-2 11°45 18°63 33°66 25°66 || Low Water. 40°3 ISS: 18°64 33°68 MSIL IM (bottom) 0 12505 18°46 33°35 25°34 |\ 12.30 p.m. ; 4 9°2 11:4 18°62 33°64 25°66 hrs. before 40°3 pi? 18°65 33°69 saat High Water. (bottom) 0 12°4 18°58 ao°D 25°42 | 2.30 p.m. 9-2 ESS 18°58 Jason 25°50 | hrs. HOae 40°3 iy? 18°67 Bea) USOT High Water. (bottom) | 0 Lt 18°59 Brae le. 25°50 4.3 : 9°2 11°6 18°61 DOLL 25°62 tie Wator. 40°3 1-2 18°66 Sor 25°76 (bottom) | It is clear from the above that at any rate at some stations a variation in salinity due to the tide alone does occur. The variation, as was to be expected, is greatest for the surface water and least for the ground water :— The maximum variation at the surface in the above experiment was 0°23; at 9:2 metres it was 0°13 and at the bottom only 0:09. Now the maximum change of salinity for the same station between February and November, 1907, was 0°81 for the surface and 0°88 for the bottom water. There can be no doubt, therefore, that a small seasonal change in 170 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY, the salinities occurs, as had already been concluded from the results summarised in the last table but one. The change due to the tide will certainly, in most cases, be much smaller than that found above. On the line Holyhead—Calf of Man it will probably be Calf of Man will probably be greater the nearer the point undetectable, and on the line Piel Gas Buoy considered is to the English coast. Nothing has as yet been said of the temperatures of the water samples. These, of course, are higher in the summer than in the winter. ‘The surface water is in many cases somewhat warmer than the underlying, but in other cases it is the same. From 9:2 metres downwards the temperature 1s fairly constant. In the case of one or two of the deeper stations there is sometimes a notable diminution in the temperature with depth, and in the case of some of the shallower stations the temperatures are rather irregular. In the shallower water this is probably connected with tidal currents. A few words may finally be said about the position of certain isohaline lines in this area. That for salinity 34 probably starts at Burrow Head, Wigtownshire, runs across to a point a little west of the Point of Ayre, starts again at the Calf of Man and runs across to Holyhead. It then crosses Carnarvon Bay, making a shght curve inwards, and then goes in almost a straight line across Cardigan Bay, ending near Cardigan. This may be regarded as a sort of mean position about which it will vary with the season, so that, for instance, the portion between the Calf of Man and Holyhead will sometimes (about May) make a considerable bend to the east. The salinity of all the water to the east of this line will be below 34. The 33 isohaline is clearly much more affected by seasonal ee SEA-FISHERIES LABORATORY. 171 changes, but the details available are not sufficient to justify speculations as to its course. The seasonal variations of salinity found in the area with which this paper deals are probably entirely due to variations in rainfall and in the amount of fresh water flowing into the sea from the land. CuemicaL DEPARTMENT, UNIVERSITY OF LIVERPOOL. 172 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. AN EXAMINATION OF THE OBSERVATIONS MADE ON THE BLACKPOOL CLOSED GROUND DURING THE PERIOD 1892 TO 1906. (Plate IV.) By H. J. Bucwanan Wo .taston. The statistics for the Closed Ground off Blackpool deal with 327 hauls made with shrimp-trawl, shank-net, and fish-trawl. Table I. is an analysis of the hauls. In three years, 1899, 1901, and 1902, no hauls were taken with the shank-net. As our aim is to form some idea of the variation in the number of young fish from month to month, or year to year, it is obviously of little value to | consider the catches of the fish trawls, which have large meshes and are constructed to avoid as much as possible the capture of young fish. We have to resort then to hauls taken with the shrimp-trawl and shank-net for results. The numbers of hauls were found to be quite insufficient to give useful results if taken monthly. They have, therefore, been taken in seasons of three months each, viz., January to March, April to June, July to September, and October to December, as will be seen on reference to Table I. The relation between the shrimp-net and shank-net in catching power is shown in Table II. The results were obtained by averaging groups of hauls taken with the two kinds of net as far as possible on the same day and under similar conditions. The averages of the values thus obtamed were then reduced to hourly catch, thus giving a fairly reliable picture of the relation between the nets in taking-power. The shank-net thus appears to be far superior to the shrimp-trawl in avoiding the capture of SEA-FISHERIES LABORATORY. ie TaBLe I. Showing Number of Hauls taken on Blackpool Closed Ground with Shrimp Trawl, Shank Net, and Fish Trawl during the years 1892 to 1906 inclusive. Yr’ly : : Totals of all nets fo tls Shrimp Trawl Shank Net Fish Trawl c ee ering p pee Jan.| Apr.| July | Oct. | Jan.| Apr,| July | Oct. | Jan. | Apr. | July | Oct. | Jan.| Apr, | July} Oct. | Ail to to to to to | to to to to to to to to to to to | peri- Mar.| June} Sept.| Dec. | Mar.| June} Sept.| Dec. | Mar.| June} Sept.| Dec. | Mar.| June|Sept.| Dec. | ods. See ete) SPH 0! O38 Oe 4s On) O PO) 0) OP ba 4 6) as ees eG at ber sol) oO or eo) Gals F Gch orl os meee) 5) #\ 6) 12 0)| o\ 11 OO 8) 7/19.) 3 hear ees 3) oO} 2 | ol] o1 4) 3) 3) 4)i4l 71.6 han meee oie! 24) 6) wi wi 4) 2) 6) 4) 81/3 | 96 gee) 12 1-431) 14 | 16) 13/14) 1/5/19) 5 | 93 | 35 | 44] 32 l134 Bega anole) ¢) ail 6) 0) ol-s | sf 7) ol 7/12) ar mepimmea| 2) 0 4) of o| 1) of of 3) 11 7] bla menies | 07) 01,0 <0] Oo} 1) 1) O| of Vl 4] oles meni 0) 466! 210) o| 0) 0) Oo 7) 6) 41) ony eee | 0 | oho) 0) Oo) o} 3 o) 2) 3) “al Piao ieee | eon U2 V0 LO) Gn OF) 2) 9 3) 19) VG 260) FAS ei CFR OF Or 2 1 1) 10) 6) 3) 4128 oN May | MOG ts 7 |) 837 OF ote 5a O21 Ol Wy a wy Oy s 2 3 Shear enon amar cle tel 6 | 29 + aprons |) kt To AO 1k OD 18), 6) 359) 36 SOF 0-17 hs 174 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. TABLE IT. Average number Average number | Average number | of Young Fishes Net used _of Shrimps per of Undersized | taken with each hour Fishes per hour | quart of Shrimps Shrimp Trawl...| 53 Quarts 6,175% 1,155 Shank Net...... Gf «4; 1,6422 2393 young fish, and this with no loss or even a small gain in capture of shrimps. The shank-net hauls were made partly with the ordinary form, and partly with the patent Bar-net. Table III. shows the relation between the TaBieE III. Average number Average number | Average number| of Undersized Kind of net used | of Undersized | of Shrimps per | Fishes taken Fishes per hour hour with each quart of Shrimps Ordinary Shank 553 2° 1 —— - 263°3 Bar Shank ...... 508°5 2°2 231 catching-powers of these two nets, the values being obtained in a similar way to those for shrimp-trawl and shank-net. It will be seen that the bar-net is slightly the superior both in avoidance of young fish and in capture of = ee shrimps. Tables IV. and V. give the average catches per hour with one shank-net and one _ shrimp-trawl respectively, of plaice, dabs and shrimps on the Blackpool Closed Ground for the four seasons. The figures were SEA-FISHERIES LABORATORY. 175 en ee TABLE LY. Showing Average Catch per hour of Shrimps and Undersized Fishes with Shank Net. Season January to March April to June July to September October to December Shrimps} Plaice| Dabs |Shrimps} Plaice | Dabs |Shrimps| Plaice | Dabs |Shrimps} Plaice | Dabs Pts. N No. No. N ¥ mi iaNo. | Pig. |. No. | No. | Pts: Pts. one ty ia 1892 0 0 0 DE eae aires all eee a eee | ee 221| 956 | 2970 1893 | 153) 236 | 770 63} 31] 86 4] 92231) 207 |) 172) 12293), S64 1894} 163] 631 | 1227 23) 80] 155 SUPE See (SUIS) |) Meese B a) pe eS a Mee asia) cof WES) ie 720s a Soule ee | tee tae 1896 | 143) 392 | 1625 1a (aol 428 af 114 |) 449°) 1141) 9390) 360 ini. OM eee hin Am hie on eh wale otals.}| 153] 420 | 1207 32) 66 || 79 6). Est |) 202.) 7 1096 111395 tso7| 13| 70| 130| 33 137; 982| 6| 26{ 32] 2) 12| 72 Meee te |) 51-752.) — | | 43) 11 Se ee c ; a eee ee cee Ee ee as 1900 ‘ 9 | 1476 @ |) 19-1 173 AG 6 (a Gah) aC hee ad eae ee OER UT Oe meen (areas a eg eee eas ee Be Ouint Pee Cowes weil i hl A eee tals 63| 43] 786 Bl) ee 127 Sey 4 7 en eR 72, Dre kee. ll ee 1903 | 103) 18] 729 5| 20| 529 64/3 |) 238. |) (214/02 2 |) See 1904 8 4 | 3634 1 SS rae esiting PU) |i Ses YR Le ES eed) ay 1905 14} 64] 707 ADL TUN Boab acti eid i meee eee ees ag BeBe re ee ee eh eee ta. Pe 4 , int. en na orn oir i corn fit, Woe ot See als 63} 29 | 1890 21, 33} 182 6H 8 BB 21) — 25-888 176 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. TABLE V. Showing Average Catch per hour of Shrimps and Undersized Fishes with Shrimp Trawl. eason January to March April to June July to September October to December Plaice | Dabs |Shrimps} Plaice | Dab Shrimp:} Flaice | Dabs |Shrimps| Plaicc | Dabs |Shrimps Pts. i Pts. Oa No | No. | Pts. | No. | No. No. | No. | Pts. | No. | No, AN fa reas 2] 310 |) 210%! 74] | 490 | | 261) ee 1 | 2419 CERT eS PUES gece eFC Re GIN Pra hf es 6 | 2916 | 3966 | 26 | 2182 | 7862 1894 | 174] 3036 | 2864 a 712 1455 |) 2. | 133] 617 |10786 1895 | 63] 751 | 2129 3/ 273 | 313 411106 | 254] 123] 2165 | $851 1896 | 36 | 2756 |15200 5 | 543 121 | — —-———— | — — | — — | = | | ——— | —_———_ | ——— | ——— | — | — | | oak 20 | 2183 | 6731 2| 459] 275 5 | 1504 | 1449 | 153] 1241 | 7479 “1897 || 24)" 326 | 4572 | 0 | 209; 102) — | — | = |) ge 1898e15}0107))| 606 || | S0e4 eager 2) 15 | 389 | 1872 | 14] 508 | 1627 110) Pees a eer IU EE) hg ae 13} 74 | 366 |) =) 1900.| “163! ‘100-; 3509 | — |)— |i =s' |) + || = ||) ee 1901} 15| 286 | 7399 1| 214] 517 0} 135 | 340 1} 130 {10280 Quintty oi to TET er totals gi} 329 | 4722 | 212 | 309 5! 423 | 859 53] 232 | 4511 1902 53} 332 | 5305 23] 244 | 2159| 3] 99 | 1301 14] 174 | 1865. 1903 | 18 | 209 |14121 2) 34| 745 6] 42] 929| 32] 20 18050. 1904: pea ecice| | oi! 40] 857]: 121 16]; 608) =a) , 1905 62] 125 | 6152 0} 59]. 391 4] 74| 499 63] 7 | 1253 POOG | evelyn ae bee 2) ties le Sel Bee 0} 196 | 2000 | |— |) )==asanam Quint |). |) tk LD TE a totals | 10}/ 222 | 8526 33} 94 | 1038 5| 85 |1067| 133! 67 | 7056 + SEA-FISHERIES LABORATORY. jar obtained by averaging all the hauls taken in the season in question and reducing to average catch per hour. As the figures are too irregular for it to be possible to form any idea of variation directly from the tables, curves were drawn through points representing the values to be examined. Fig. 4 is a curve drawn through points corresponding to the average catch per hour with shank- net of dabs in the four seasons. To eliminate the small yearly difference in this variation, the whole period of fifteen years was considered. Fig. 3 is the curve of the same values for the shrimp-trawl. These show that the maximum catches of dabs are made in the winter, from November to February, and the minimum catches in the summer, from May to July. The very low position of the curves in June and July should not be taken as repre- senting the actual values, but as indicating the probability that if an average were obtainable for the catches taken at this time, it would be lower than the averages for catches either before or after it. Figs. 1 and 2 are the curves for yearly variation in number of plaice caught per hour on the ground with shrimp-trawl and shank-net respectively, each curve representing the same season throughout the fifteen years considered. The curves have not been drawn through the points representing the actual values, but have been smoothed in the same way as were the monthly averages for the Mersey Banks (see page 179), so that irregular variations are disregarded and _ the general tendency of the figures shown. Both sets of curves show a marked decrease in the number of plaice taken per hour on the Closed Ground since 1892. This decrease is least visible in the curve for April to June. Other curves have been drawn, but are not included, as they show littl: sign of any regular variation. Thus, the curves for hourly catch of shrimps are so irregular that no deductions could hourly catch of dabs show that the fluctuations in m caught are mainly confined to the winter seasons, Octol to March, being then about four times as great as in summer. | . ha 7 7 ~e-¢ a J ms st 7 a ; : ~ > a d I a ah : _— i i hh ~ = - > 4 qe ; 6 BI | - vod 061-668: oe x LAU SU BUYS 009 UODIDIIDA [DUOSNeS 008 Sqvd -anoy sed SA8yIJ0) aboiaay ‘PUNOTD poaSod]) joody so] q ‘SOG6I -3G8! ZU ~mMnst qwsiaus | eu ie NA 0988 SLOMAS Wal eat) 139d Say DI abniany 0096 : puncoab PaISO}d [Sod S507 Q osle ‘GO61-G68) FMD] CUHIUS ‘UOLDIADA = |MUOSDES SGVq -snoy sed SoyUdLD) abpiday :puNdAH PaSOjs jOOgY IvIg 00.,.66., SG, 26.96, S6. CO. 6., OO. [Wx GOP VOM ows abnueay 3 L | . ° £ <= oSig :STaUUDYD. AoSdow - = 7) <= LTH g. re Ale ‘S061 —- G69! pmMosy, quays SaIleS Puy saliva a ‘anoy seq Sayoj0d ene ‘Syug & SEA-FISUERIES LABORATORY. 179 AN EXAMINATION OF THE EXPERIMENTAL HAULS MADE IN THE MERSEY ESTUARY DURING THE PERIOD 1892 TO 1906 INCLUSIVE. (Plate V.) By H. J. Bucwanan WOLLASTON. The present paper deals with the records of the experimental hauls made on the Mersey Banks and in the adjoining Channels, by the L. and W.S.F. steamer “ John Fell,” and the New Brighton police cutter. The material consists of several hundred sheets, dealing with nearly 800 hauls—there being 260 hauls made with shrimp-traw! nets, 70 with fish-trawls of various forms, and 13 with shank- nets, all on the banks; also 281 with fish-trawls, 163 with shrimp-trawls, and 3 with shank-nets, all taken in the channels between the banks. It was evident on examina- tion of the records that the number of hauls made with fish-trawls on the banks, and with shank-nets both on the banks and in the channels were quite insufficient to afiord reliable conclusions. The shrimp-trawl-net hauls, both in the channels and on the banks, and the six inch fish-trawl- net hauls in the channels, are, however, sufficiently numerous to warrant statistical treatment, and the results have some interest, especially with regard to the variations from month to month in the numbers of plaice and soles on the banks. The method adopted was as follows: Every haul was separately reduced to an hourly catch, that is, to take a simple case, if the haul was of two hours’ duration the result was divided by 2. From all the hauls in each month so reduced, an average haul was calculated, giving the numbers of plaice and soles caught per hour’s fishing. The observations were, however, made rather irregularly, and so in order to get a more reliable average catch per hour for each month, the whole period oi fifteen years 180 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. (1892-1906) was considered, that is, for instance, all the average hourly hauls for January were added together, and a new average, giving the number of fish caught per hour’s fishing for the month of January (1892-1906), was thus obtained. Similarly, to find the yearly variation, which was only possible in the case of the summer months, owing to lack of data for the winter, an average hourly catch for the six-monthly period, May to October, was obtained in each year, and the variation of this average from year to year was studied. Curves were drawn through points corresponding to these averages, and since it was found that these points were too irregularly dis- tributed to give reliable results, they were modified in the following manner:—The values representing the average catches were arranged in chronological order, and the first and last were taken as correct. For each of the other monthly averages a new value was substituted, obtained as follows:—The average catches for the month in question and that immediately preceding and succeeding it were added together and the sum divided by three. This is the well-known statistical device of “taking three-monthly averages monthly.’ In some cases the figures thus obtained had to be again treated in the same way before - it was found possible to draw a really smooth curve through the points, showing distinct maxima and minima. The following figures, those for average catches of plaice with the shrimp-trawl net, will serve to show the method. Original Figures. First Smoothing. Dia Masi. . 72 ... (taken as correct) ... 72 HSER ae aca Lea Pat cigs Mar. ...... 182 ... oe = 193 April ...... 94... ee — 144 May ..02% TES Be ARIE tee are &e. SEA-FISHERIES LABORATORY. 181 This method may appear somewhat artificial, but is not so in reality to any great extent, as it merely means that the ‘values of the numbers for the months immediately before and after each given month are allowed an influence in determining the new values for that month. Now if we proceed to construct curves showing the variation in the average hourly catches of plaice and soles made per month on the banks, we notice a distinct similarity in the shapes of these curves, 1.e., where there is an increase in the number of plaice, there is also an increase in the number of soles, and vice versa. We do not, however, know whether the rate of increase is the same in the two cases, that is, for instance, whether a 10 per cent. increase in plaice would correspond with a 10 per cent. increase in soles. Now, in order to find whether this rate of increase is the same or different, we may take, instead of the actual numbers of plaice and soles caught, the logarithms of those numbers, and the curves constructed from the latter values show the relation between the rates of increase and decrease, that is to say, if the two curves have the same shape and height the rate of increase is the same in the two cases. This has been done (figs. 1, 2) for the monthly variation of plaice and soles on the Mersey banks, and also for the monthly variation of average hourly catch of soles with shrimp-trawl and six inch mesh fish-trawl. We are now in a position to attempt to draw con- clusions from the results obtained by the above methods. The data are not sufficient to warrant any conclusion regarding yearly variation except in the case of numbers of plaice and soles caught by the shrimp-trawl net cn the banks in the summer months. The curves plotted from these values seem to indicate a complementary relation- 182. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. ship, plaice increasing as soles decrease, and vice versa (see fig. 4). c In the monthly variation there is, on the other hand, direct correspondence between the hourly catches of plaice and soles on the banks with the shrimp-traw] (see figs.5, 6), plaice increasing as soles increase, and at approximately the same rate (see fig. 1), though the period of greatest abundance is slightly earlier in the case of soles than in that of plaice, the maximum for soles being in August, while that for plaice is in September. Regarding plaice taken in the channels no very reliable conclusion can be drawn, the data being too scanty, but the greatest catches seem to have been made at the same time as on the banks (see fig. 3). In the case of soles taken in the channels, the curves of average catches with shrimp-traw] and six inch fish-trawl show distinct relation to each other, both as to the position of the maximum catches and in rate of increase (see fig. 2), that is to say, if large soles increase, small soles increase in approximately the same propor- tion. The maximum is somewhat earlier for soles in the channels than on the banks. In dealing in the future with separate yearly returns, the curves given here for monthly variation might be regarded as the standard forms, and the curve of monthly variation for any single year, if it differs widely from these standards, might be looked upon as_ rather exceptional. Of course these curves may differ con- siderably in different localities. | The tables of monthly averages, and the curves of monthly and yearly variation mentioned above are appended : — SEA-FISHERIES LABORATORY. 183 AVERAGE CATCH PER Hour oF PLAICE AND SOLES ON THE Merrsty Banks with SHRimp-TRAWL. 4 = a pb 2 oO 3) Q a a = | ; = 3 | os 5 ® ® 8 5 & 4 a > n= Q gio] s 3 a | 3 o| 8 = a a | @ ea fe) soe) e cle cms wellsas coclotae es SOMTaS ete. SOTO Or |e Plaice Deke cl 2 Rea pe ta Am ee Be A Oe ce AOD WE er 0 |......1 Soles 81 | Plaice 0 | Soles 1894 {217 |134 |295 {178 |661 |402 |170 [556 [571 4225 |......)...... Plaice Mo GOs las Sl 38) 20r 16 AO | Sea ee oe. Soles 1895 = eee 25 | 57 | 55 | 59 |586 1456 |2315/813 |189 | 62 | Plaice ee) 0 1/18 6 | 24 | 29 5 8) 0 | Soles 1896 ee einer 279-317) (a68. 1914 1206 1.2.0.) 120 leeks Spice a aN 4 0 a Vy kO 23 ieee Ub ocele tees WOlES _ 2 git BESS Bee Bee Oe aise. SE BON SS PTZ Ss. sehalhateetlesa ee. Plaice Lope Bie pees See ZO cscs) AG dary SOM 4 ala ltt Soles = Ls Ee aoe 8 1 1 {100 | 45 |661 |888 |423 | 80 1 | Plaice 8 foe eee 8 ew tart 26 2a 63 yoke 1 O | Soles ete Seis ne. olan see loeeca te cdts ie cccalsoe nels oust oliedsad Plaice on Teel SE Ais SPU Se Bae Ed OE REG) Be ES NC JOU: Sy eee tee Ree pee ed Soles Cale |e Eee) ee | 8 rs ene PRY Ceo eee ee eet Oe, Rann ea? Ree ae ae A Plaice eh hia bc kee) Setar Meigs ia ee (Bae MSR Bs Eg SP eee ee i Ua A Soles 5 ol eS SS Be Sea | ay SP a) Sa A 459 4 | 44 | Plaice BED SE| Soe So) Se, See ee i hie Sei AON SANDE (ieee heb BAR Ip 0 | Soles 1905 |2807| 20 Pa Or ast a a IO 20a Sr (168) -25°:|- 9 "| Soles 1906 | 21 | 88 |163 {103 | 53 |-55 |......|...... Deniers baleen 5 | Plaice Set 45 LED ELE (663 437. to ntieels acess if tof ae Boe ee 35 | Soles 184 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. AVERAGE CatcH PER Hour oF PLAICE AND SOLES IN THE Mersey CHANNELS WITH SHRIMP-TRAWL. September November December eeeeee weeeoelseoerceertesceecs{[sosreecieccessi|secoeeoleevaneiseseesissoeesiseeceesiseseeesisesens eececelecceecelesccece|sseeeslescoevi(esceee{esseceieereerriseocseosiseeseeeieseeeeisesecne eoeeces eeeccelecececei|soevecieesecelsesecosi|seveee|sseeesiceseesiseseeveisesensieoseesiseseee eeeeeetecereecetecacces{ececeeelsecooceleoseesiereeoco{eeseeeiceseesiseveeeiseseseiseeeee eeeeselecececelscceesisesesslessees|ssssevisesseosiseseesiseseesisseesesiseoesesisesens eeecccleseceeeieceeseiesseceiseveeeisseeesieseses eevee sle cose eieseceesiesreeeriseeeesieeseesisseses eeecceleseeesisecseesiesecseel[seseseiseceselseseee ee Oe SEA-FISHERIES LABORATORY. AVERAGE CatcH PER Hour or PLAICE AND SOLES IN THE . witH 61n. FisH TRAWL. 185 Mersry CHANNELS February September October Mesiaimelasemmeéelocwocelovceaes, © fF Cem fo BIO fF © eema Fy IO. levececeoaeesve eeesetleoeeetiseseesisestece weseestlersecesiseseecsiseeceveleeseseriseeesseceereri/scoeserseei|seeeoseeveoe wesesticeseeelseesecel|secasel|seeese|seeesseseeere|s-eveeeeetieeeeascesere were eslesesesissceesiscceese|sscesrisesesenesest|sosesesesi|sesrcooses scene wees eseoeeeel|eeoseseere seeceeelseseeeiserevr|serceonel|seeteerieneeeseeese08 eerecesoceserlsocesroee sere eeleeseselsevesslesseasiseeseeriseosseseesees ee rec eecesees|seecsoeeer/svesce0ese00 weeesselsecoseseiseseee|s»esece|seseerieesecsesseses sess eelseeeseeissesesiseseesiesescelseseeseseoveetisccoseoseeet|ersenoessest|seseeseer|sencesserce oe eeteeele esse elise eeeei|sseseeeiseseeslsessesesesseriseceseers|seeesesecrerrlenesceees/seseeevreseee weeceelseseceeiscesesisesensisoesee sesoesser|seceeoseecerr|seveeresri|srve0eees000 wees eels esses iseesesisseseeisscess| - j-§ C2 J|eeseesessiesesescesseeriseeseceseer|sesessecvese November December Perec ereceosseosisovene Cores ecoseerl|oosees ee reeerceseeeel[seeees eereoereeccceerlscceee eereoserevrerl|sccooee eereesovececstsesene eerteece eres rl|eecece CO Ce ee eoeoe rer eoee|sevcee sees e ele ese asissseeeisesses|seesssiessesrressseesiseesesessisesenesesestisseeseeee|seserseeveee wees eelse esses isesessisereesiseseeostisscecesssessisessesserr|seeoeseseeeriensceresserlsevessosceee eerecceecseesl|sesecseoriervresseecsere wees esiseesssicesessieseses|seesesiseseercessess weeseeeleeseeeisesees|sreersiseesessisessessevesee eereeserrleoceeeecrene ee de eroerleesessocsese ee eeertiseseee sees lsesess Ce seseseleseoes (UU | mw | FO FF @ 8 FE fh Fo lee eeeseoecerlesceesoes eoreesescoerl|ecoecs eoseee eoveesesrerecclseosens eoceeceoesserleoseee eoeerecereoecr|enescs eeceoseeeserl|seccens wesseesieseese)| VY tf FF fF CF fF BREF | hed tQD Joe veesecvsessiecsecsors ordinary 6in. mesh trawl. + Cr ed Nore.—Where there are two numbers in one line in any square the second is the average hauls made with a fish-trawl having pockets and tails of 6in. mesh, the other that for the f AN INTENSIVE STUDY OF THE Alaa PLANKTON AROUND THE SOUTH END OF THE ISLE OF MAN. 186 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. By W. A. Herpman, F.R.S., anp Anprew Scott, A.L.S. INTRODUCTORY. The objects of this detailed investigation into the Plankton of a limited marine area are twofold :— (1) To study the distribution of the Plankton as a whole and of its various constituents during the year, and (2) To attempt to arrive at some estimate of the representative value of such samples as are collected in our plankton nets. Of the fundamental importance of plankton work in regard to fishery questions of a wide nature there can be no doubt, and of the absolute necessity of the determina- tion of the value of samples and of arriving at some estimation of their representative nature there can be still less difference of opinion. In former reports* we have shown that our results around the Isle of Man and in other parts of the Irish Sea show great diversity in the plankton, both quantitatively and qualitatively when considered according to locality or according to date but in all these former reports we have felt that fuller information might enable us to reduce the apparent chaos to order, and might reveal some method or definite sequence in a distribution which seemed indefinite or irregular. Consequently we have endeavoured during the last year to make our observations as frequent, full * Twentieth Annual Report of the Liverpool Marine Biology Com- mittee, Dec., 1906; Presidential Address to the Linnean Society of London, May, 1907 ; and Twenty-first Annual Report of the lL.M.B.C., Dec., 1907. SEA-FISHERIES LABORATORY. 187 and detailed as possible, and the result is that we have now at our disposai a much larger number of samples than has ever been collected before in such a limited period from the Irish Sea—possibly a greater number of samples than has been obtained in one year from any other part of the British coasts. The total number is 885 obtained from our northern portion of the Irish Sea bounded by lines drawn between Holyhead, Liverpool, Barrow and Port Erin, in the year 1907; and of these the majority, 650, are from a very limited area in the immediate neighbourhood of Port Erin. At the South end of the Isle of Man, where these gatherings were taken, there are very important fishing grounds which are frequented by trawlers from Lancashire and from Ireland, as well as by the Manx fishermen. This, as well as the circumstance that we have there, within a few miles, a sheltered sandy bay, an exposed rocky coast, a narrow strait and an area of open sea with depths reaching to 70-80 fathoms, has led us to consider Port Erin a very suitable locality for a more exhaustive or intensive study of the Marine Plankton than has yet been attempted on our coast. Previous Locat Work. The Liverpool Marine Biology Committee started a scheme for taking weekly plankton gatherings in this district of the Irish Sea as long ago as 1888, and although as the result of weather, changes in the staff and other varying conditions, many gaps have been left from time to time in the series, that aim has been constantly before us, and the practice has been kept up intermittently. y 20ims. ,, ~ 10 fms. (20-10). 3. % > 30 10ims. ~,; * 10 fms. ae 0). (open to ) 4. ; >» > 30 fms. _,, » A arial (30-0) Weighted open net (A) and two surface nets (Al and A2) along with shear net (Sh. 1) at 15-20 fms. Weighted open net (B) and two surface nets (BI and B2) along with shear net (Sh. 2) at 7-8 fms. (These each }-hour hauls; the one set taken immediately after the other). Mill water bottle at 20 fms., strained at the time. Re 20 fms., strained on shore. Locatrry B:—8 miles out W.N.W. of Bradda, over 30 fms. 1. Hensen and Nansen nets let down to 30 fms. and hauled up 10 fms, (30-20). Wp oe Be * 20tmisa | e. oy 10 fms. (20-10). a in 2 - 1Oidms. 415; i 10 fms. (10-0). 4. Nansen (alone) _,, 3 oOims: 45, ., to surface (30-0). Weighted open net (C) and 2 surface nets (Cl and C2) along with shear net (B1) at 7-8 fms. Weighted open net (D) and 2 surface nets (D1 and D2) along with shear net (B2) at 15-20 fms. (These each }-hour hauls; the one set taken immediately after the other), Mill water bottle at 20 fms., at 10 fms., and at 5 fms, ail SEA-FISHERIES LARORATORY. 193 The fixed stations at which observations were generally made are shown in the adjoining plan (fig. 1), where I and II indicate off-shore stations, respectively five and ten miles from land; and III, IV and V show the along- shore stations, one to the north towards Niarbyl, one to the south near the Calf Island, and one in the “ southern sea’ off Spanish Head—all, except II, in water of much the same depth, about 20 fathoms. The region covered measures about ten miles from east to west (out to sea) and rather less from north to south (along the coast), but the area investigated was really very much less, being confined to the above-mentioned stations from which plankton samples were taken and the in-shore waters of the Bay. OFF PORT ERIN -ho:M: Ow ees ee ee, Fic. 1.—Plankton Stations off Port Erin. The usual practice, in our work on the yacht, was this: At each station, after taking the bearings, depth, &c., we first lowered two vertical nets, the Petersen- Hensen and the Nansen, to a depth of 20 fathoms, pulled them up slowly through 10 fathoms, and then closed them by “messengers” run down the line. This gave us 194 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. samples, taken vertically with these two very different nets, of the organisms present in the water between 10 and 20 fathoms. After that three ordinary horizontal open tow-nets exactly alike in all respects (size, shape, mesh, age) were put over—one (A) with a weight attached was allowed to sink to a depth of about 10 fathoms, from which it gradually rose as the ship went slowly ahead; while the other two (B and C), unweighted, remained continuously at or just under the surface and worked side by side hke a pair of sharks or porpoises swimming in our wake. ‘These two last nets ought, if there is any uniformity whatever in the plankton even in the most limited areas, to give similar results, and of course they did so in many cases. The purpose in taking the two similar surface nettings side by side was to show this, and also to test the reliability of the sample; for it was usually considered a more valid sample when these two nets agreed in their evidence. Where, under the circum- stances stated above, the gatherings differed notably, there must have been some accident in the working of the nets or some irregularity in the distribution of the plankton, such as, no doubt, will sometimes’ be encountered when traversing the edge of a swarm of gregarious organisms; and it is important to get some evidence as to how frequently such accidents or irregularities may be met with. For example, on April 2nd, at along-shore Station III, the two surface-nets used together gave 17 c.c. and 42°5 c.c. of material respectively ; on April 9th, at Station I, 2°5 and 8c.c. respectively ; and on April 24th, at Station II, they gave 7 c.c. and 15 c.c. respectively. On many occasions, of course, they were very similar, and on some almost identical in their catch (see examples given below). Each of these horizontal nets was hauled for 15 minutes. SEA-FISHERIES LABORATORY. 195 The net A (which may be called the weight-net) is of use as having traversed a wider range, 0 to 10 fathoms, so as to sample all the water above the zone traversed by the vertical nets, and it frequently, and in fact usually, obtained a larger gathering and showed a greater variety of organisms than either the deeper, closing (vertical) or the open surface nets. On some occasions, at the ‘“along-shore”’ stations (e.g., 2 miles off Bradda Head) hauls were taken with a new “shear-net ’ made on the principle of the Heligoland “Scherbrutnetz” (Consed International—Rapports et Procés-verb., vol. 11, p. 62, 1904). This was used as a mid-water net—being lowered to a depth of 5 to 10 fathoms, where, through the action of the shearing plate, placed like a vertical otter-board, it remained even when the ship went ahead at a moderate speed, and so formed a most efficient instrument of capture in waters where the ordinary net cannot be towed. The mouth measured nine feet in circumference, the net was over ten feet in length, and being formed of rather coarse mesh caught quantities of the larger organisms of the plankton such as Sagitta, Medusae, Ctenophora, Zoéas, the larger Copepoda and some young fishes. The variation in the bulk of the catch on different days with the same net, used so far as was possible under the same conditions, was very remarkable. The accompanying diagram shows graphically the range in quantity of the total catches with each kind of net during April, 1907. The Nansen net catches ranged in quantity from 0°5 cc. to 164 c.c., the Petersen-Hensen from 0°5 c.c. to 645 cc., the weighted open tow-net from 5°5 c.c. to 41 c.c., the surface open tow-nets from 1 c.c. to 42°5 c.c., and the shear net from 11 cc. to 785¢.c. The black columns in the diagram (fig. 2) are drawn to scale, 196 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCLETY. and so give a true representation of the proportional bulk of the largest and smallest catches with each net. We have considered it unnecessary to print in this first report the details of the nearly nine hundred tabular forms containing the results of the hauls, but we shall give various lists extracted from these tables, and curves derived from the lists, and we shall also reproduce a certain oss tha tS - iass : sd 1h +0}. | hs E 5) oy Wis £ t Bah, H vas ‘ yA 80} aot : : / b * $ — — — pues 3 = Sr hs = ‘ fw uy s ah ite Fig. 2.—Showing by proportional columns the range in quantity taken by the various Plankton nets in April, 1907. s number of the sheets of records as samples of different nets, dates and localities. ‘The complete series of sheets are deposited in the Zoological Department of the University of Liverpool and will be available for consulta- tion there, and may possibly, if it be found desirable, be printed in a future report along with the results of a further year’s work. sail 7 SEA-FISHERIES LABORATORY. 197 TotaL PLANKTON THROUGHOUT THE YEAR. We give now, as the first summary statement from our Forms, and in further illustration of the great quantitative range shown by the gatherings taken on different days, the following record of the “ total plankton,” reduced to the average* per haul for each individual day :— Date. Average per Haul. Date. Average per Haul. Jt. AS ae U;27c.c! 1 Ot | a ene 10 cc. eS iS ore loins ae Tiames: ai Oe aroed at Goes Oia. 1 ¢)c. Ss Renee opefe oo Rac eilee enone LO: > ss =). 27S ER eee ae 2S Many eS: ik eats } eee eee Od, eee Sa. ave rua: ee 012 eee sya pe Aa ee ciate vere 6 ,, ae Sea rues dbl = keto eee es 20° = 5 ast ee ae ee 145 ,, oe, PL Uirar sate 1325. 5 2 72 ae eee es eae ld weccepenne sets: Le. is SUT) 80 eee cee Lia; Ouly FeO as. heee st ects Ae, -: AR Eee a lael Bi PO ano See SD) 5 A 2 ae 42°5 ,, SA bal rae ce ete Ae PAS Go nrttecincpindys 23 ee Se oils seer sheet 1s ees Amie aN a ics ae nae On Oe. » 14... coseqeee kp a Br gM) Teton at ateacec tates 7 a 99, DEN no acinar yume eed Te be A rt PA a PARAL os Novi: 4 “See ooeeee 11 * eg Sl WRW BRE OMe EA es PR i= 8 <5 6. LD yi eect meuedonte Bea | ». 16° 282s 1b pe se dowdneucinecs 4:5 ,, 59 2D Seas ceeeeaeee Poh ale = Foy Or gO tacosteac eerie Srawiss Dec. 12 3..caedaaee eae Sieh Me bes aaah erat Nears : er 9 20) tee i, ae Si) n MSG PAE etic erat icc le SS jo || Zo Gesaheeeeneee |B days Ro ie LDR hoe ete date ier de, oe jo | BO” Seccscaeeeeeees [aa Fr From this list and the unsmoothed curve shown below (fig. 8) it is seen that the greatest bulk of plankton in the water is in April, when the total catches in the day reached an average of 51 c.c. per haul. Other lesser elevations are seen in June with 20 c.c., and August with 25 c.c. The catch in some individual hauls runs a great deal higher than these averages, the top score being the Nansen net on April 4th, with 164°5 c.c. The spring maximum in the amount of the plankton is clearly due to a great and sudden increase in the amount of Diatoms present. ‘lhe other rises seen later in the year, as in June, August, and to a slighter extent in October, are less marked, and are less clearly due to one cause. | SEASONAL VARIATIONS IN THE PLANKTON. The above remarks indicate, what has in fact long been recognised, that the amount of plankton varies to some extent with the season. We shall now reproduce some of our Forms giving the SKA-FISHERIES LABORATORY. 199 results of hauls showing special features of the plankton at different times of the year. Form No. 10, representing the hauls taken on an off-shore station, on April 5th, shows the condition of affairs during the spring maximum of Diatoms. It will be noticed that 14 milhons of one species, Chaetoceros contortum, were present in one haul of the Nansen net. The total number of Diatoms in that haul was nearly 17 millions, including two milhons of TVhalasstosira nordenskioldiz. . Comparatively few Copepoda and other large organisms were present. It will be noticed that the two surface gatherings of this date were moderately alike, the same organisms were present in both, although one net had, in some cases, about twice as many as the other; but still the hauls were of the same general type and the quantities were, in most cases, not very different, showing that one ean get a good general idea of the fauna by such hauls, but that one cannot depend upon their being minutely representative. They may represent, apparently, some- thing hke double or half the quantity of organisms obtained in neighbouring hauls. For comparison with Form 10 we print Form 71, showing a similar series of hauls taken late in August from a neighbouring staticn. Here there are practically no Diatoms present, there being only a very few individuals of Biddulphia mobiliensis. On the other hand, the Copepoda are more abundant than they were in April. For example, compare Ozthona similis, where only tens, amounting at most to a few hundreds, were present in April, and thousands (reaching eleven thousand in the weighted net) were in the August haul. Other interesting differences will be noticed on comparing the two Forms. 200 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 10. Off-shore Station II, April 5th, 1907 ING@GiMISOG) (skids. cttcenssatem tee cere Surface. Surface. Hensen. Nansen. Depth im fathomis.:-..,--.<. cece 0 ) 20-10 20-10 @aschim ccni i \ ike. see wan hehe 9 12 12-5 100 Asterionella bleakeleyi ......... a — eae 15,000 Biddulphia mobiliensis......... 3,000 4,000 1,000 15,060 Cheetoceros contortum ......... 33,000 78,000 286,000 14,000,000 om decipiens '.5...c5-0.. 6,000 6,000 6,000 50,000 ] GELRES i ina son nresiecoiine — — 2,000 50,000 a Giademia wae tecenacs — — 1,000 — Coscinodiscus concinnus ......... 2,000 4,000 1,000 15,000 Coscinosira polychorda............ -- —- 4,000 Tk. Rhizosolenia semispina ......... 1,000 2,000 4,000 i> Thalassiosira gravida ............ 1,000 1,000 8,000 90,000 A nordenskioldii ... 21,000 52,000 26,000 2,000,000 Eauderia borealisi-...s.ce se osseee se 1,000 2,000 20,000 600,000 Ceratulina bergonii ..............- — — 1,000 = Ceratinmy muncarneeeieeadecere — 1,000 1,000 bit ai LUSUS Ae tonaiedeacisoseaone 1,000 3,000 1,000 = Pe UEIMOBy acta caiestes eens ot 1,500 3,000 1,000 a Medusoid gonophores ............ 40 20 — — Plutei of Echinoderms ......... 500 1,000 — = Sagitta bipunctata ...........666. — — ~- i” Larval Polycheta ................66 — — 4 == Ne Gran ay?) 363 Fish Eges rr wa 93 Generally speaking these ecONe hold good for many of the series of hauls not only in the Bay, but also outside; see, for example, Forms 20 and 21, below. _ It is also interesting to note that of these two series of hauls taken in exactly the same spot on adjoining days, SEA-FISHERIES LABORATORY. 205 the total amount obtained is much the same, but 1s made up of rather different constituents, Biddulphia mobiliensis, Chaetoceros contortum, and some other forms, being more abundant on the 9th; while C. debile, present on the 9th, is altogether absent on the 10th. The very large number of Echinoderm Plutei on April 9th is noteworthy; their occurrence is very sporadic; they were present again in large numbers on April 19th, when 1,000 were taken in the haul corresponding to I. A. on April 9th. But, on the whole, the resemblance between the two hauls is more striking than the differences, the list of organisms is very nearly identical in the two sheets, and the general run of the numbers is for the most part the same. Another interesting comparison, in this case of two separate but not distant localities taken practically at the same time, is seen in the Forms (20 and 21) that are given here for April 10th. No. 20is from off-shore station I, five miles N.W. of Bradda Head, while No. 21 is from the second station ten miles off land along the same line. Both are in the open sea and at both the same set of nets (Hensen, Nansen, Weighted, and two Surface nets) were used, within an hour; but in the first locality the total bulk of the plankton caught was 104c¢.c. while in the second locality it was only 39 c.c.; and it will be noticed in running the eye down the figures for the different organisms that the five-mile station yielded far more in the case of Diatoms and Dinoflagellates and fish-eggs, but less in the case of Copepoda. The total Diatoms amount to over 35 millions at five miles as against 324,000 at ten miles; the total Dinoflagellates is 55,000 at five miles and 13,000 at ten miles; while the Copepods are under 3,000 at five miles and nearly 5,000 at ten miles. The general run of organisms present is the same in the two cases, although the total numbers differ so much. P 206 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 17.—Port Erin Bay, April 9th, 1907. ATGu ised Saetooole not LA ILA LBl LB2. LBS ToBI Chteh: in iciem.!. vic.stesss 10°5 8 7 6°5 4 8°5 8°5 Biddulphia mobiliensis 45,000 7,000 8,500 2,500 3,000 7,500 2,500 Chaetoceros contortum... 39,000 © 38,000 70,000 31,000 50,000 100,000 50,000 * debile ...... 9,000 — 2,000 — 2,500 2,000 — 3 decipiens ... 7,500 3,500 8,500" 4,000 2,500 5,500 3,500 6 HOLES. cacte «ie 1,500 — 1,000 — 1,000 — 500 3 diadema ... 2,000 — 2,500 1,000 1,000 500 ~—-1,500 a criophilum — — — — — 500 _— Coscinodiscus concinnus 3,000 2,000 2,000 1,000 2,000 3,500 — Ditylium brightwellii ... ae _- 500 —- 250 ~—-1,000 — Rhizosolenia semispina... 500 -1,000 1,000 2,000 1,000 3,000 I07Ge Thalassiosira gravida ... 100 100 — -- 250 500 500 x nordenskioldii 12,000 13,000 5,000 14,000 11,000 30,000 17,000 P 53 subtilis ...... 1,000 6,000 6,000 4,000 5,000 5,500 4,000 Lauderia borealis ......... 2,500 500 2,500 500 500 3,000 750 rochiscta sp sexescesesce — — — — 20 25 25 Acanthometra sp.......... os _- —- “= 50 50 — Ceratium furea............ 300 _— 500 -— 250 200 500 - PUSUSs | wo ee steno 100 ~—:1,000 500 ~—:1,000 500 ~=1,000 1,000 5 tripos. |! vee. ss — 1,000 500 —- 500 250 500 Peridimium' sp: \s.cs-5-.-02 — 1,000 500 100 250 300 500 Medusoid gonophores ... 75 70 10 27 30 30 20 Plutei of Echinoderms 1,000 ~=1,500 500 500 500 — — Larval Polychaeta......... 75 75 20 10 30 50 30 SCUMUtrariar carne ess ek 100 100 — “= 100 100 100 Crabizoea Hh eccersenauae 5 a — 1 -- ] — Podon intermedium ...... 20 12 10 10 20 — 10 Evadne nordmanni ...... 5 a -— _: — 50 — Calanus helgolandicus ... 25 6 10 10 10 15 10 Pseudocalanus elongatus 70 175 150 250 190 125 140 Temora longicornis ...... 20 35 20 5 5 45 20 Centropages hamatus ... -- — 5 5 5 10 10 AGartia, Clatisuye ses... 2: 60 40 10 40 15 60 45 Oithonasimalisntey-c,c: 140 85 55 40 35 100 70 Anomalocera juv.......... — 2 —- —- 10 oo -- Paracalanus parvus...... —- = = 15 — — = Copepod nauplii ......... 11,000 3,000 3,000 1,500 4,500 3,000 2,000 » metanauplii ... — 20 — — ae = —- sie h pA Meee epee eee 1,100 375 160 475 165 400 300 Barnacle nauplii ......... 400 175 75 275 220 140 180 > Wicypris stage |... 10 6 6 12 7 5 Oikopleura sp. ............ 900 600 550 700 630 — 750 680 Fish Eggs :—Rockling... 1 1 == 2 _- — — Com. Dragonet ......... 2 1 a —- 1 — — COd Haina pens srcesitcee sae a 1 1 —- — — — —) Green iCodix. d.saasese eo. 1 — a a — 2 —_ BUD sees mente chen 1 -- = — — — _ Wihitiniet.eo 52, tote 2 — a= 1 — 1 a Red Gurnard ......... — 1 — — — — _ Topkniotiie. s:-deisec. nee 2 —- — — — — = Dae olietastanhercaet sate 1 1 — — — —_ = pail Tike) cake weecese arte 1 — — — _ = Splatiwarccsesks Geese cass — 1 1 o 1 - Young Fishes— Larval Gadoid ......... — — 1 — —_ _ Larval Pleuronectid ... — == — ear 1 SEA-FISHERIES LABORATORY. 207 18.Port Erin Bay, April 10th, 1907. Net used, Surface ......... LAI ITL.A LBl I. B2 I.B3 TP Bie Vik BZ Beanel i C.CM. ...;........ 14 8 A 8 8 10°5 12°5 Biddulphia mobiliensis 5,000 1,500 1,500 500 3,000 1,500 4,000 Chaetoceros contortum 15,000 20,000 20,000 15,000 50,000 90,000 20,000 be decipiens ... 2,000 — 1,000 2,000 5,000 6,000 - — UP: ie — — 500 500 500 500 —_— 45 diadema ... 150 — 1,500 500 —_ Coscinodiscus concinnus 2,000 1,000 1,500 500 2,000 500 1,000 Eucampia zodiacus...... — — Rhizosolenia semispina 500 — 500 500 3,500 1,000 1,000 Thalassiosira gravida ... _ -= — -— 500 500 ° —_ a nordenskioldii 3,500 10,000 4,000 4,000 32,000 28,000 6,000 E. Seuslice........ 8,000 6,000 3,000 2,000 6,000 9,000 4,000 Lauderia borealis ......... 500 250 = 500 4,000 1,000 500 menehiseia, Sp. ............ — 50 — — — — — Acanthometra sp.......... 30 _ 150 — 50 25 — Ceratium furca............ — — 100 — 250 250 150 a PMA Oo sven och 1,500 250 500 -— 250 500 200 is i ne 200 500 =. 2,000 — 250 500 250 Peridinium sp. ............ 500 100 500 500 500 ~—:1,000 150 Medusoid gonophores ... 150 3 60 70 50 15 180 Plutei of Echinoderms 100 100 - — 250 500 — Sagitta bipunctata ...... — a _ — — 2 _ Larval Polychaeta ...... 150 5 60 a= 50 — 120 MREEATID 2... 2.0.00. 200 150 50 — 100 — 200 3) ss a — = — = i — 5 Mysis stage of Crangon 5 _— 3 = ] — — Podon intermedium ...... 20 — 10 30 — — 15 Evadne nordmanni ...... 10 2 20 20 10 — 15 Calanus helgolandicus ... 60 30 100 30 35 — 60 Pseudocalanus elongatus 780 30 300 150 50 35 480 Temora longicornis ...... 100 30 70 50 60 35 100 Centropages hamatus ... 20 10 30 4 10 — 15 Acartia clausi ............ 70 30 80 50 150 30 90 Oithona similis ............ 350 100 200 100 250 300 200 Anomalocera juv. ...... — 10 10 — — 25 — Paracalanus parvus ...... — — — — — — 60 Copepod nauplii............ 11,500 500 2,500 3,500 500 ~=1,000 =12,000 a re 2,250 75 750 900 350 100 = 2,000 Barnacle nauplii ......... 850 50 460 270 150 10 ~—«:1, 230 oe cypris stage 12 4 10 2 1 10 Oikopleura sp. ............ 1,800 250 ~—«i1,300 950 700 230 2,000 Fish Eggs—Rockling ... 1 6 — — 1 8 “= Common Dragonet .. = — ] — _ 1 1 ES eet See 1 — — — 1 1 1 LE el — 2 1 — 1 1 — LL eee 1 1 — 1 3 _ — eee 2 — — — — 3 — _ CSU eee — — — -- —- 3 — 7 Le Se pa a — — — — 1 _ Long rough dab ...... — — —- — — a 1 Pee ao ics .e — — — — — — 1 es a ee 2 — = — 1 — — Young Fishes— Pleuronectid ............ 1 — — — — — — ’ P \ Nansen Weight : 208 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 20.—-Off-shore Station I, April 10ti, 1907. INGG AMSEC ce Macnrea dts via Uars toate Surface Surface Hensen Depth in fathoms’ ............... 0 0 20-10 20-10 Cateby In) Goin, > 6 iiinees ester baits 12 18°5 ] 58°5 Biddulphia mobiliensis ...... 5,000 5,000 500 1,000 Chaetoceros contortum ......... 39,000 28,000 19,000 1,200,000 rus debile: a yiekene. ses —- — — 75,000 * decipiens. ........... 2,000 1,000 500 62,000 a Sociale; “J .tvavnsbsss a —- 4,500 75,000 om CONGS Die sas eaoe eames ae — 1,000 25,000 Hh CIAMONNS) oved.e% oes — —- 25,000 Coscinodiscus concinnus ...... 1,000 1,500 500 =: 12,000 Ditylium brightwellii ............ — — — 6,000 Kucampia zodiacus)............ _- 150 — — Rhizosolenia semispina ......... 1,000 — — 12,000 Thalassiosira gravida ......... — —- 500 —- 12,000 i nordenskioldii... 58,000 135,000 15,000 1,600,000 3 SUDEMIS . consccess 3,000 1,500 — 12,000 Lauderia borealis ...........006. 1,000 1,500 5,000 150,000 Ceratinm ‘furca ies scescsestesens — 1,000 — = ; EUISUIBW ee Guten dpletee's cee 3,000 500 — — at LT UDOS. (bee vice vs.clerssie ester 4,000 3,000 500 — Pericamiam’ Sp ierce es. cin sss cessonse 1,000 1,000 — 37.000 Medusoid gonophores ......... 30 80 5 26 Plutei of Echinoderms ......... 1,000 1,000 = — Sagitta bipunctata ............... — — - — Tomopteris onisciformis......... — — —_ 1 barval Polychaeta: |i.1c..-ssc0c — — — 20 CrabozGea ooo. Vossidvass.pssecooes 2 1 — — Mysis stage of Crangon ...... — — —- 1 Nephrops, Ist stage — — — 3 Podonintermedium -.3..-..0-- — — 1 — Evadne nordmanni ............ 10 10 — — Calanus helgolandicus ......... 25 1 3 23 Pseudocalanus elongatus ...... — — 18 130 Temoralongicornis.:..:......-... 25 — 5 56 Centropages hamatus ......... 30 40 — 2 INCALEVA 7CLATUSU IAs cistetcals cs oe sis eine os 500 500 8 14 Oithona ssimiliisy he. tcsasenerees oe 30 2 47 Anomalocera uve, ».¢sea/--+---\ 170 500 —- — Copepod marplity Nex. «-1as..ce se 0s 3,000 2,000 500 — ve metanauplii ............ — — a re 5. UUW tees. seesuasbetes+ 500 — 25 130 Barnacle map, ens sche. a0 L0 10 2 25 #5 CY Pris (Stage j\..3....0- 2 1 — ] Oikoplourai spi eccce meee wenn 270 300 18 80 Fish Higgs’: Haddock... -....... + — — — COG Ie i secctceis ate aeeegwir caer 5 31 = ne reenvGOG: mrcscecessapaceses 15 33 — ag Com. Dragoret \...5-2.+40- 5 3 — — WV GG. i ks ocak se bib temaar 60 89 — 4 Pocket. teres, cenaeetoaee — 1 — —— Grey Gurmard ) siccennnacere — 6 — = MSU ry i. iatcetsl hme eins ate ce 3 23 — — UO PEMOP Sa neenee-bess san agen 1 3 _- — Brille, nie cne seas seeioay deat 1 — — vee Red -Gurmard °c. isv.cesees- 1 — — a “Bail Blake: 2.0. RAAB Ae 9 2 — — DN oR narra ane ones Sets) 2 4 — ee Scale fish lo uasanp sees se 3 1 — — Long Rough Dab ......... — 1 — = SOTA vistsce sunita ace mre Moana 3 6 — = Young fishes—Gadoid ......... — _— — 1 10-0 15 7,000 26,060 2,000 1,000 1,000 1,000 17,000 10,000 1,000 3,000 500 80 500 one SEA-FISHERIES LABORATORY. 209 21.—Off-shore Station II, April 10th, 1907. _ 2) S20 202 eee eee eee Surface Surface Hensen Nansen Weight Peps in fathoms ............... 0 0 20-10 20-10 10-0 SST Ce 1 a er 7 8°5 Oo 9 12 Asterionella bleakeleyi ......... — — 100 ae (a= Biddulphia mobiliensis ......... 100 100 100 250 ae Chaetoceros contortum ......... 1,000 4,000 12,000 180,000 2,000 pe Geel Mens 2 )....6:... — —_ 2,000 11,000 —— ts SEN AEO Secs sciccaae.c< — — 100 5,000 ee i RPE eo wie nanan Son he — — —- 4,000 — Coscinodiscus concinnus ...... 2,000 1,000 100 1,000 1,000 Ditylium brightwellii ............ — — — 1,000 — Kucampia zodiacus ............ — — = 500 aed Rhizosolenia semispina ......... — == 100 1,000 aa ” stolterfothii ...... oo — — 100 — Thalassiosira gravida ......... — — 50 1,000 = ie nordenskioldii ... 1,500 3,500 10,000 58,000 1,000 “ StI Uo 58850242 1,000 — 50 5,000 2,000 Beaderia DoOrealis ~.......5...<. 100 = 1,500 9,000 — Ceratulina bergonii............... — — — 250 = JESS Do 500 100 1,000 ue alee a SSRI EE eee 200 500 500 = oko a8 vo Soe Be ae 6 geen ies 1,000 500 500 1,000 1,600 ICPUNEMT SP)... 20.2240. 20.00. 000¢ 500 1,000 500 3,000 2,000 Medusoid gonophores ......... 40 10 —. 16 150 Plutei of Echinoderms ......... — — 100 500 1,000 Sagitta bipunctata ............... — — — 6 24 Tomopteris onisciformis......... — -- — 1 2 farval Polychaeta ............... — — — 20 aay 2S i ee 150 — 50 — 1,000 Mysis stage of Crangon ...... = — — 5 Podon intermedium ............ _- — i — a Evadne nordmanni ............ 10 — — ie pot Calanus helgolandicus ......... 6 2 3 36 150 Pseudocalanus elongatus ...... — — 3 240 450 Temora longicornis ............ 10 30 4 30 200 Centropages hamatus ......... 10 10 — = 2 ee i 880 570 2 15 62 SmpMona StmMilis ..........-0s.000. 30 100 2 115 375 Anomalocera juv. .............-+ 500 750 — = 400 Pepepod nauplii .......5..-2..0+-- 1,500 2,000 1,000 3,000 5,000 “3 Metanauplii ............ 36 150 _ 20 350 ee CE ee Oe ae ale eevee ee 360 500 10 500 250 Barnacle nauplii ..........:..0000+ 10 40 5 60 330 a cypris stage ......... 3 5 1 3 25 BMOPNCHES SP. -occeccdecnscacons 1,360 1,800 22 400 1,000 Fish Eggs— AE athe psig jeeps vire 16 13 — — — TAME CSEMATO 2.0. 0005 000'o- 8 5 — — 1 Reet WO) 05.262) dale one 12 ai — == 1 lo EE aS ere — 6 — — 1 ree ae ee 2 —- — — — a SO ee Ree oer 1 1 3 2 5 L111 er Ree ee ied 3 1 — a ae WES Fiasid nas och es = tases — — — 1 — Young fishes—Gadoid ......... — — — -- 5 a ver C LA) " 910 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. As representative examples of the series of hauls taken at the two offshore stations (I and II) early in April we give here copies of our Forms 10 and 12. These are both localities in the open sea, well out from the land, about five miles apart, and under, so far as can be seen, practically the same influences and conditions. They exemplify several points we wish to elaborate, viz., a certain amount of similarity between the surface hauls, the weighted net at ten fathoms showing as a rule a larger catch than the surface nets, and the Nansen vertical bringing up more than the Hensen. But the point we specially wish to illustrate from these Forms is that the plankton fauna on these two occasions had a similar character, although the numerical results may be far from agreeing. The total Diatoms at Station I are over twelve millions and at Station II over seventeen; in each case it is the Nansen net that caught the millions both of Chaetoceros and of Thalassiosira. The total Copepoda at Station I is 1,534 and at Station II 2,247, but the numbers in the case of some of the species are of the same ‘order’ on the two Forms—Calanus is in units, Centro- pages and Anomalocera in tens and Acartia in hundreds 99 in each case. Finally, the conclusion one comes to from the inspection of these Forms is that much the same organisms are present in somewhat similar proportions; so that although it is possible to discuss the general character of the fauna and the relative abundance of different groups, it is not possible to use the numbers as the basis of calculations as to the quantity of any group, or of living things as a whole, in any large area of the sea at a particular time—the results arrived at might easily be 50 per cent. wrong in either direction. To show—what will be readily admitted by all who SEA-FISHERIES LABORATORY. 10.—Station II, April 5th, 1907. (bo S35) SS eee Depth in fathoms ......... Ppeteh im €.CM. |........-... Surface Surface Hensen 20-10 Nansen 20-10 Asterionella bleakeleyi Biddulphia mobiliensis Chaetoceros contortum é decipiens ... 5 HERES! do ssc5fse = diadema Coscinodiscus concinnus Coscinosira polychorda... Rhizosolenia semispina Thalassiosira gravida ... ea nordenskioldii Lauderia borealis ......... Ceratulina bergoniil ...... Ceratium furca ............ <3 BHSEEG) a seale ac 03s ss Plutei of Echinoderms Sagitta bipunctata ...... Larval Pelychaeta ...... Une ee ln ee Mysis stage of Crangon Larval Nephrops, stage 1 Evadne nordmanni ...... Calanus helgolandicus ... Pseudocalanus elongatus Temora longicornis ...... Centropages hamatus ... Anomalocera pattersoni Acartia clausi.............+ Copepod nauplii............ Zs metanauplii ... Barnacle nauplii ......... Oikopleura sp. ............ Fish eggs :— Ue A Long Rough Dab ... g Ue DO es ecane sust ch eerte Young fishes :— Plaice ... eS Ld He DD OO me bo —" eon) 1,000 286,000 6,000 2,000 1,000 1,000 4,000 4,000 8,000 26,000 14,000,000 50,000 50,000 15,000 90,000 2,000,000 600,000 10,000 2,000 912, TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 12.—Station I, April Sth, 1907. ee ee —~ Surface Net tSed yin: ieecees name ae Depth in fathoms ......... Gate hl wmicicniey esses soos ce Surface Hensen 20- 10 Asterionella bleakeleyi Biddulphia mobiliensis Chaetoceros contortum iu adebile’ a2: 3 Ks decipiens ... 3 sqciale ...... * TOELES 2... cx06 Coscinodiscus concinnus Coscinosira polychorda... Ditylium brightwellii ... Rhizosolenia semispina Thalassiosira gravida ... » nordenskioldii ni subtilis Lauderia borealis ......... Leptocylindrus danicus... Ceratium furea |....0., 20... Bi FUSUSHcesccreeease ue CLIPOS HS ciharevee Medusoid gonophores ... Plutei of Echinoderms Sagitta bipunctata ...... Larval Polychaeta......... Craio'Zoea ices) siseaeiiesosn's Mysis stage of Crangon Larval Nephrops, stage 1 Evadne nordmanni ...... Calanus helgolandicus ... Pseudocalanus elongatus Temora longicornis ...... Centropages hamatus ... Anomalocera pattersoni Acartia clausi..........se06 Oithona similis ............ Tsias clavapes.....:...:++ Copepod nauplil............ iH metanauplii see 45 AALVnes cnceresut neem Barnacle nauplii ......... cypris stage Oikopleura SION Ces lowaine he Ascidian eggs .... Fish eggs : :—Rockiling .. Common Dragonet Sailfluke .. : Topknot .. Long Rough Dab . DBO eee pein ets oaseinlas Deala Mish Wives dace ynt Geeae fishes :—Gadoid... 100 100 186,000 15,000 100 100 100 100 lee lel | | NOD —— Or 60,000 10,000 3,000 120,000 15,000 500 500 500 3 31,0 100,000 00 00 4,000 6.0 00 1,000 1,000 1,000 37,000 7,000 or PLT TTT EET TET] Perr l wS] ee] law! | wleol | | Nansen Weight 20-10 10-0 73 21 20,000 2.000 1,650,000 9,000 7,500,000 138,000 150,000 27,000 _ 50,000 1,000 20,000 is 50,0006 1,350,000 132,000 - 20,000 450,000 3,000 1,000 Eon _— 300 — 500 _— 500 8 100 _— 100 2 10 3 10 — 4 2 34 — 2 3 1 40 500 30 200 — 100 4 30 — 10 1,000 — 20 150 _— 4 6 350 — 1 — 3 — 6 — 10 1 ae SEA-FISHERIES LABORATORY. 213 have had any experience of plankton work—the marked effect of the size and mesh of the net upon the resulting catch, we give here from Form 47 the hauls of two surface nets and a shear net taken off Bradda Head on April 23rd; and we add also another shear-net haul taken later the same day a couple of miles off, between Bradda Head and the Calf Island. It will be noticed that the two surface hauls are very much alike in quantity and constitution, and the two shear-net hauls are like one another and very different from the surface hauls. The shear-net has retained no Diatoms and no Dinoflagellates, but has caught far larger quantities of the larger organisms, such as Medusoids (Hybocodon prolifer) 4,500 against 10 and 100 taken in the surface nets at the same time, Sagitta 200 against 2, young Shrimps 1,800 avainst 5 and 8, and young Norway Lobsters 1,600 against 1. In the case of the Copepoda the shear-nets have large hauls of a large form such as Calanus, but much smaller hauls of the smaller forms such as Acartia and Ovthona. Similarly the shear-nets have not retained the larval and young Copepods, but have most of the fish eggs and all the young fishes. Some of the differences in further detail may be due to the depth at which the shear-net was towed, but the broad lines of difference are clearly seen to be caused by the nature of the nets. In order to determine more definitely, without any disturbing influence due to depth, the difference in catching power between the large open-meshed shear-net and the much smaller ordinary tow-net made of fine- meshed silk, we tied a tow-net to the frame of the shear- net so that the two would work together side by side, and we show here in Form 105 the results of two such double hauls. In the first place, it will be noticed that the shear-net 214 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 47.—One mile W. of Bradda Head, April 23rd, 1907. Shear* = Calf Island to Bradda. INGt: tise yc Ne hee hee. ae ake Depth in fathoms ............... Catch in ¢c.cm. Biddulphia mobiliensis ...... Coscinodiscus concinnus ...... Peridinium sp. shaeaiewie se Pleurobrachia pileus Se case Medusoid gonophores ......... Sagitta bipunctata ............ Tom opteris onisciformis ...... Larval Polychaeta ............ Mab rar as WAL Bee ee lassie deere Ora bizoeay ca titeescestecwesecntes Mysis stage of Crangon ...... Nephrops, Ist stage ......... Byvadne nordmanni <........... Calanus helgolandicus ......... Pseudocalanus elongatus Tem ora longicornis ............ Centropages hamatus ......... Anomalocera pattersoni ...... Acartia, ClAUsit 1. .2.deveceiecesecet Oithowa similis el ee. 3. she. MetridiaTucens <1.) cult eee ces a Candacia armata ..............- Copepod mauplaiy een. ie ..0-s «6 9? HUW s daeteaionsies sie alce's s Barnacle nauplii ............... 9° cypris ice A Soacnabe Oikopleura sp. Fish eggs :- — Spee ee Young fishes :— Gadoid ..... teeeeeeeeeeeaeee wpand-celf! Me 5... ca. sseseciace's Surface 0 12°5 Surface 0 13 Shear 10 75°5 Six lL lesSl il | | OD 2 6 70 7 1 1 SEA-FISHERIES LABORATORY. 915 105.—Mid-Channel, September 12th, 1907. Net used ..... fy EA eee Shear A Tow-net A Shear B Tow-net B Depth in fathoms ......s.c.s00e 10 10 20 20 Were E CLOT) coces doce. cccenwae 18°5 11 13°56. : Z Biddulphia mobiliensis ...... — —_ — 130 Chaetoceros contortum ...... — — — 1,250 ae Cele Seek — ao — 3,700 x decipiens 73.3.3.55% — 3,000 20 3,500 ad SURIAIC® So beccccsce — — — 750 a PEEOS Ar nec hereteee — 7,500 — 23,000 Pa convolutum ...... — — — 1,300 “ GENSUIMN Stas case —- 2,000 — 1,500 i. diversum ......... — — — 400 Subuile 3.5. 222.4.06 -- 13,500 — 5,000 Coscinodiscus concinnus ...... = 500 — 600 EAQTAEUS . } 25:25 — 4,500 — 4,000 Ditylium prichtwelltt ...:.. <. —- _ — 120 Eucampia zodiacus ............ — 500 = 130 Rhizosolenia semispina ...... = 80,000 500 165,000 > shrubsolei ...... — 500 50 625 a 21 CG Sean ee — — — 3,400 a stolterfothii ... — 500 — 1,500 SELIBCTA? «1 -.qe- ct — 250 — _ ieee: OPC RS Bs ccveecoescus — 500 — 1,000 Leptocylindrus danicus ...... _ —_ — 600 Asterionella japonica ......... — — — 120 Cerahium fasas ~.....05:73s00- — 500 50 250 be (lt 1 ee ee Oe ee 10 5,000 - 50 3,000 PEERPMTEE SP). <.)00000 00500 c00i00 — 500 — 120 SEC@EHISCID SP: 6-12.60 cesisve se ce = 100 20 _— Medusoid gonophores ae 45 1 55 3 Sagitta bipunctata ............ 200 5 135 1 Larval ee. Suideiaish Pov ee 25 1,500 -= 250 * Mitraria ’ PES a toes — 2,000 — 120 WEISS eco conc vrs kante deans Z, r = — Mysis stage of Crangon ...... 2 = — 1 Microniscus calani ............ 70 — 10 _ Calanus helgolandicus ......... 2,600 110 275 20 Pseudocalanus elongatus ... 300 33,600 285 6,250 Temora longicornis ............ 10 —_ 2 1 Centropages hamatus ......... 6 5 3 2 (RGAFCIE CLAUS. «..2050cr0cues.s 0058 350 3,640 450 200 Ua 60 2,840 65 1,200 Microcalanus pusillus ......... 10 200 10 2,500 Paracalanus parvus ............ — 100 20 160 Copepod nauplii ............... 30 24,000 75 - 4 PUNE d a ovosseostaes vie se 60 12,500 275 — Gasteropods, larval ............ 10 1,000 — 500 Lamellibranchs, ,, _ ........- — 1,000 _ 370 CMO PIGUEA APs 2663423105 2 neesnee 25 1,000 50 140 PRIGIAD OLEB 2000 csescces cise 25 1,500 25 600 216 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. A and its tow-net at about 10 fathoms caught nearly twice as much material as the same two nets (B) worked at about 20 fathoms. The further point is that in each case the tow-net retained the Diatoms, the Dinoflagellates, the minute larval forms and the smaller Copepoda which had escaped the shear-net, while the latter caught more of the larger organisms, such as Medusae, Sagztta, Microniscus, and the large Copepod Calanus. The number of organisms in the tow-net in each case is enormously greater, but those in the shear-net bulk larger on account of their individual size. Taking the last item on the lists as an example, the obvious explanation of the numbers would be that there were more Ascidian eggs at 10 fathoms than at 20, and therefore tow-net A caught more than tow-net B; no doubt both shear-nets being so much larger caught still more, but the majority of the eggs passed through the wide meshes, and only a very few (25) were retained accidentally in each case, probably through being entangled in the appendages of larger crustacea or through the blocking up of some of the meshes. THe SurFace Nets. The two ordinary open tow-nets with a mouth diameter of 144 inches, and made of silk No. 9, with 94 threads to the inch, were towed side by side on the surface of the sea about 50 feet behind the ship for fifteen minutes on each occasion. In the great majority of cases it may be certain that their catch was limited to the upper two feet of the sea; and yet notwithstanding the uniformity of the conditions the results were in many cases very different. The following lst shows the bulk of the catches on the various occasions when the two nets were SEA-FISHERIES LABORATORY. AG. used together, and although some show identical results, asvon April loth, 19th, 22nd, August 21st, 24th, 27th, September 6th and 20th, and in other cases amounts which are very nearly the same, such as l6c.c. and 155 c.c. on April 13th and April 19th, 9c.c. and 9°5 c.c. on April 16th, 10°5 and 1lc.c. on September 12th, &c.; still other cases are very different, such as 14 and 1, 8 and 2°5, 17 and 42°5, 1°5 and 7 c.c. respectively. Net B Net C Net B Net C mepril 3} §-== 86.6), *... (25) ie. Aug. Zi— 15 ese) 57 2—17 2 42°5 21— 3 3 4—14 Beet can 23— 9 6°5 5— 9 ate Foal 23— 4°5 4 8—20 me cet 23-—— 5 2 9— 8 cee i AO 24— 2 iS 9— 9 eee lice 24— 2 2 10—12 4. 185 26— 1 2. 10— 7 Sse SO 27— 1 1 11—165—...._—s«:10 28— 3 £ M15... 5 28— 1:5 3 13—23°5 ... ~=16 28— 1 2 13—16 Sesh ako 29— 4:5 3 13—205 ... 24 Sept. 2— 2:2 1 15—11 ee) Co 3— 2 15 15—10 ae 3— 2°5 15 16—12°5 i... 5 4— 2 2°5 16— 9 mee 5 4— 2 3:2 18— 8 ce loo 6— 15 0°6 18-235 :. ATS 6— 0°3 05 19—18 Sees Sees 6— 0-7 0:2 15) AG 6— 15 15 22—11 Boies 2b 6— 1 0°7 22— 95 §... 95 9— 85 4 7p Wy Ae) re 10— 1:2 15 23— 9 arya a 11l— 2 Le Z3— 85. =). 65 11— 1°7 2 24—20°5 ... 155 J— 5 3°3 24— 7 15 12—10°5 11 25— 5°5 4°5 13— 3:2 4 25— 2°5 20 16— 75 2°5 25— 8 75 17— 15 3 26— 65 9 18—12°5 13°5 26— 4 45 18— 2°5 45 27— 6 8 19— 2 2°5 27— 3°5 11-5 20— 4 6 27— 7 13 20— 5 5 20— 2°5 5 20— 2°5 3 Even when the results are very much alike quantitatively they may be very different qualitatively, 218 TRANSACTIONS LIVERPOOL BIOLOGICAL 45.—-Along N. shore of Calf Island, April 22nd, 1907. Netinised!s sch chess eeacoee Depth in fathoms ......... Oatehem lec. uaa ces eae 10-5 SOCIETY. Biddulphia mobiliensis Chaetoceros contortum Coscinodiscus concinnus ... Lauderia borealis ............ Ceraitiuma furca: ss css beces ts Bt PUSUSi Ee asia sank er 9) ETIPOS «oes eee eee eee Peridinigm, Spijnesssesses 004 Pleurobrachia pileus ...... Medusoid gonophores ...... Sagitta bipunctata ......... Autolytus prolifer ......... Tomopteris onisciformis ... Larval Polychaeta ......... CMaGrariah ay Set BY ama gt nett ok Crab zoea «....... Mysis stage of Crangon ... Nephrops, Ist stage......... ee 2nd stage ...... Podon intermedium ......... Evadne nordmanni ......... Calanus helgolandicus ...... Pseudocalanus elongatus Temora longicornis ......... Centropages hamatus ...... Anomalocera pattersoni ... ACartia, Clawsi seats. ee eRe as Oithona; simtlis <..i5.0.has-—. Anomalocera juv. ............ Me tricia licensty a ecce see cece Copepod matipliie..-csne. +1) a UV coc teetoh ts sawsea: Barnacle nauplii ............ 5 cypris stage Oikopleurayspie an. sec Fish eggs: Rockling......... Wihitine 2.00 a. cope tase Crey-Girnatd som...) - ed (Gurrcards ers Green Cod. 22% 4ssceeuen oe Haddock Com. Dragonet Cee Spotted Dragonet ... Bib tegen. Young fishes: Sand-eels ... GaGoray cinco scce eck Pleuronectid. ....2:).2.% Butteriish eee —l tl eeal wl I | teal | | io as) ee a Cabs ts stat llc eee eae LL Salt lrlel lll I ew8 SEA-FISHERIES LABORATORY. 219 and it is by no means always the two hauls that are most alike in bulk that agree best in the kind and number of organisms. On reflection, it will probably be agreed that it is unlikely that, with the large, varied and irregularly scattered population that we find the sea to contain, two nets should often catch the same quantities of the same sets of organisms. Consequently a result like that obtained on April 22nd (Form 45), where the two nets caught precisely the same amounts, and where the lists of organisms constituting the hauls are almost exactly alike both in kinds and numbers, is interesting. It will be noticed how different the catch of the weighted net (exactly similar to B and C but ranging through a lower level of water) was on this occasion. ‘The shear-net being of much larger size and having a much coarser mesh naturally gave very different results. It is not comparable with any of the other nets. As an example of a case where two similar nets, hauled side by side on the same occasion, gave very nearly the same amount of material, but where the kinds and numbers of organisms present in the catch when examined were found to be very different, I give the following lsts of the contents* of the two surface nets after a 15-minutes haul on April 13th, 1907, at Station III. The one net contained 16 c.c. and the other 15°5 c.c., but these amounts were made up very differently in the two cases. For example, it will be seen that in the net C there were no -Balanus nauplii and no immature Copepoda, while thousands of both were present in B. Then, again, in B there were very few adult Temora, while in C practically all the Temora were adult. The lists will show other * Only omitting those organisms of which fewer than ten individuals were obtained. 220 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. points of difference. We may add that in the haul of the shear-net, taken at the same place and time, there were 1,380 larvae of Pectinaria in tubes along with 5,400 Balanus nauplii, and many other organisms. Net B=16c.cm. Net.C=15°5'%c.cm, Larval Polychaeta .............6 650 Siete 0 IBALANIS MIAN PIG os fics auveler ess cact ¢ 3,000 ae 0 55 CYPIIsS Stage \.....:..... 50 cae 0 Copepoda nawvpliit. ) ws)... cers ess 7,000 ee 2,000 y; TMEV, 5 octet cach oak eeewain 13,000 os, 0 Calanus helgolandicus.......... 100 ee 6 Pseudocalanus elongatus ...... 850 ioe 500 Temionalongieormis ie. .pae sen n- 2,470 ie 4,750 Oithona jsimilisc?. castes nee cete nts 100 a 50 ACATtIA CLAUS ii. 52.4 nncsecchenas 250 cae 200 Centropages hamatus ............ 0 mee 200 Coscinodiscus concinnus ......... 8,000 ae. 14,000 Biddulphia mobiliensis............ 40,000 ian 70,000 Rhizosolenia semispina ......... 1,000 ap 3,000 Lauderia borealis .2.............5-- 1,000 “a3 0 Thalassiosira nordenskioldii ... 2,000 ete 7,000 is SU DEUS eosin os 6,000 sie 0 Chaetoceros teres ....5...:...000+-- 0 Bae 1,000 Perici ium SP. keke elon vce os 500 Sse 0 PUGET oH an amrete unas amte teint 500 oe 1,000 Oikopleura tsps .cct s.bes cevest oe 2,000 ime 150 Medtisoid sisi iatns accensmacsues | Soup 924 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The Copepoda are remaining fairly constant, while the Diatoms, having passed their spring maximum, are falling off rapidly. On Forms 16, 19, we give the results of hauls taken on the along-shore station III, off the Slock, on two adjoining days, April 9th and 10th. The two surface hauls are very unlike in quantity, although practically the same series of organisms is represented. Such numbers as 37,000 to 1,500; 4,000 to 250; and 19,000 to 550 indicate a considerable disproportion. The surface plankton, then, if we may judge from these two samples, had fallen on April 10th to less than half what it had been on the previous day. But if we compare the two hauls taken on April 10th, we find that the second net towed simultaneously with the first, but at about a fathom below the surface, yielded a much more abundant gathering. On looking into the details one finds that all the Diatoms and Ceratiwm tripos are more numerous in the deeper haul, while the larger organisms—Medusae, Larvae, Copepoda, and Oikopleura—are more abundant on the surface. Some of the Diatoms showed a great increase below the surface, the extreme case being Chaetoceros contortum with 120,000 at one fathom to 1,500 at the surface. On the other hand during the later summer we met with cases where the Copepoda and other larger organisms were much more abundant in a zone below the surface. Here is an example (Form 84) from off-shore station IT, on August 27, where the weighted net brought up 75 c.c. all three nets as against 1 c.c. in each of the surface nets being alike and used simultaneously. The relatively large numbers of Acartia, Pseudocalanus, and Copepod Nauplii. will be noticed. The two surface nets on this occasion yielded identical quantities, but the detailed SEA-FISHERIES LABORATORY. 16, 19.Three miles off Slock. Depth in fathoms Catch in ¢.cm. Coscinodiscus concinnus Rhizosolenia semispina Thalassiosira nordenskioldii 3 Lauderia borealis Ceratium fusus Peridinium sp. Medusoid gonophores Sagitta bipunctata * Mitraria ’ EOE ZOG yeaa Sides cnc enc < Wea Mysis stage of Crangon ......... Larval Nephrops, Ist stage Podon intermedium Evadne nordmanni Calanus helgolandicus Pseudocalanus elongatus Temora longicornis Centropages hamatus Acartia clausi Oithona similis PEHOUTAIOCET A JUV. <5 .s00c0050ss06s Copepod nauplii Barnacle nauplii CO Oe eeeoe see ee eres ese see ececereoee - decipiens mance - ; teres Ste tilis: so ese « 3 PLUP OS boeus veledewcink ces ee eer te eor essere ee eeeesereeee ee ee reer ese ssee sees eee sees rons eee eer rere ps ceee Se i were eee r sere er ec - WUE fencer crn etc SeeeP os ss CYPTIS SALE so... 6020.00 Oikopleura: SP. iciiieesscdveses hits Fish eggs— SUC NNS fo Fas vie nein slieitenate Grey -Curmard, = .cr...cec0st-0 Common Dragonet re ee ey ‘ALLS 3 ae See Sail Fluke DENG RE Coe Oe ae SEE ae ele Long Rough Dab Cod eee eter eee serene ee Woplaiat: .thrinione Se) Pisco yi t....00ssieva Ce 11,000 37,000 4,000 7,000 21,000 1,000 1,000 Hh 8,000 6,000 6 100 9 12 13 (16) April 9th 0 8,000 1,500 250 3,500 150 1,500 500 2,250 2,000 (19) April 10th Ee ee eee" Biddulphia mobiliensis............ Chaetoceros contortum 12,000 120,000 8,000 500 5,000 300 78,000 3,000 9,000 200 1,000 90 226 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. figures for the species are in nearly every case different, although, as we have pointed out in other examples, they are of the saine “ order.”’ 84.—Train Bank, August 27th. Deptbpimitabonys yy y.ssccesceteee 0 O Weight Catchisinec-Cmida. stk sss sceeeeeererece H 1 74 Chaetocerossteresic...ss-een eee: 30 50 —— Coscinodiscus concinnus ......... 40 75 — Coscinodiscus radiatus ......... — — 200 Ceratiumy LUSUS®...ceacesees sseacane 50 250 — 5 tPUPOSS Sates naseraceceetaels 150 600 400 MPO CHISCLAIS PD i-cs2s seinscienss solders 40 100 100 Sagitta bipunctata .....0.<....+ 3 1 27 Crabizoea Mecca austse uadeteestere _- — 4 Mysis stage of Crangon ......... —- —- 2 Calanus helgolandicus............ 5 4 | 200 Pseudocalanus elongatus ...... 80 70 3,000 Memoradlongicornis eens. 10 20 500 Centropages hamatus ............ 30 10 100 Anomalocera pattersoni ......... 4 — — Nicartia Claisin terete. cscs ccetesc: 550 500 24,700 Oithona (similisey. nue desses ones , 15 — _- ilistasclawalpesml sine ctenacnes cease or 30 30 — Parapontella brevicornis......... [ — 3 — iRaracalanus Patvillsiees.sceeseeee: 20 15 o Copepoda upline eee. ase 9.000 7,000 26,500 Bais are UV oc Ml aR ncaa se stra Be wee 2,000 1,500 7,000 Casteropods larval) saseues-se-s0.- 50 150 200 Fish eggs—Rockling............... —- 1 1 ASCIATAM GCSES icles ceetiacinccee canes 2,500 1,000 2,400 CoMPARISON OF DEEP AND SuRFACE HAULS. We have shown in the previous section that im some cases (April) the surface gatherings contain more Copepoda and larval forms, and in others (August) these larger organisms are more abundant in deeper zones (see Forms 19 and 84). When a comparison is made between the three similar open tow-nets which were worked together for 15 minutes at a time—two, at or close to, the surface (0 fathoms) and the other weighted so that it was lowered to a depth of about ten fathoms, and gradually. rose, as the boat went slowly ahead, to a depth of a SEA-FISHERIES LABORATORY. 92.7 fathom or two below the surface—it is almost invariably found that the weighted net, with its wider range through the deeper layers of waters, gave a larger, and sometimes a much larger, quantity of organisms. The only exceptions to this rule are on some occasions in April, when the sea was full of Diatoms and the surface nets gave very large hauls, equal to or even exceeding the deeper ones. But even during the Diatom maximum in April some days showed more in the weighted than in the surface nets. For example, on April 10th, at along-shore station III (Form 22), the surface gave 11°5 and the net at one fathom 19°5 e.c., and the total Diatoms were 27,000 in the former and 188,000 in the latter (see also Form 19, same date, above). 3 Such numbers as 18, 18, 29; 3, 3, 6°90; 15°5, 16, 23°5; 9-5, 9-0, 19°5; and 9, 11, 18 are frequent. On April 25th, the numbers are 9°90, 4°5 at the surface and 20 in the deeper net. In some cases the difference is even more marked, as, for example, on August 24th, at off-shore station IT, when the surface nets gave respectively 2 and 1-5 c.c., while the weighted net gave 16¢.c. The increase in this case was due to Copepoda being more abundant in the lower zone, especially Acartia clause (23,000), Orthona semilis (1,500), and Copepod nauplii (70,000). Other similar results were obtained at the same locality on neighbouring days. Here is a haul (Form 38) ten miles off shore, in April, where the two surface nets gave very different results and the weighted net did not exceed them in quantity. The bulk of the catch in all three nets was Copepoda both young and old. Ovkopleura is rather evenly distributed in these nets, there being roughly 3,000 in each. The shear-net haul was taken on the way in, half-way between the Calf Island and Port Erin, and shows an extraordinary 2998 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 38.—Off-shore Station II, April 18th, 1907. INGE MUISCGL) ewdec ped cuhedwnetocds Depth in fathoms ......... atte hi am. (CIM. 2. sian eotesete Surface Surface 20-10 Do Hensen Nansen 20-10 Weight 10-0 . Biddulphia mobiliensis...... Chaetoceros contortum be debile: sessieb3d¢ 6 GeCipeEN Serre aes. i sociale: | .isd.5. 6% Coscinodiscus concinnus ... Ditylium brightwellii ...... Eucampia zodiacus ......... ibauderia boreallisiee re. se 4.6 Rhizosolenia shrubsolei 5 stolterfothii... Thalassiosira gravida ...... As nordenskioldii__ Leptucylindrus danicus Ceratitiny urcay Sys. kiesene: Pes EUSUIS | = ou _ oO feature of this occasion was that the Hensen net, hauled up from 14 fathoms, contained 150 specimens of what is probably a new species of Leptopsyllus, while the Nansen 930 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. net used at the same time, and at the same depth, on the other side of the ship, caught twice as much material but not a single specimen of the new Copepod. ‘The surface nets are also somewhat divergent in their results, while the deeper weighted net has caught a very much larger quantity of material, the greater part of which is clearly made up of Copepoda both young and old—about ninety- five thousand in all. RESULTS OF THE VERTICAL HAULS. The two vertical closing nets we have used from the “ Ladybird” are the Petersen-Hensen and the Nansen, both of which have now been thoroughly tested, and have given on the whole good results. The ring of the Petersen-Hensen net is 19 inches in diameter, and the opening at the mouth into which the brass lids fit is 7} inches. The opening of the Nansen net (figs. 5 and 4) is 14 inches. As a vertical closing net we prefer the Nansen to the Petersen-Hensen. It is lighter and less complh- cated (a matter of some importance in a rough sea), more easily manipulated, less liable to failure in action, costs less and generally catches more. The brass cylinder at the lower end is, however, too small, and might be improved in other ways. These two vertical closing tow-nets are obviously not comparable one with the other. Their dimensions are different, and the results of the hauls are usually also very different, the Nansen net almost invariably catching more than.the Hensen. The maximum amount for the Hensen is 64°95, while the maximum for the Nansen is more than twice as much, namely, 164 c.c. These two nets were not used for the purpose of obtaining results that would be comparable, but were used for the purpose of testing the SEA-FISHERIES LABORATORY. | 931 nets to see which was the more efficient and convenient, and also for the purpose of obtaining corroborative evidence as to the distribution of organisms by means of a second and different net used at the same time. Consequently, the results obtained from the two nets cannot be summed, but must be treated separately. The usual plan of working at the off-shore stations was that, after Fic. 3,— Nansen net going down open. Fic, 4,—Nansen net coming up closed, ascertaining the depth, these vertical nets were lowered simultaneously to within a fathom or so of the bottom and were hauled up through the lower ten fathoms of water aud then closed by means of the messengers. Thus, the Hensen and Nansen nets brought us up samples of the fauna in the bottom ten fathoms, for comparison with the 9232 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. fauna of the upper zones of the sea obtained by means of the surface and weighted open tow-nets. In many of these hauls during April (see Form 10, p. 211) the vertical nets, although they had traversed a very much smaller area of water, brought up a very much larger number of Diatoms, for example in the case of Chaetoceros contortwm——14,000,000 in the Nansen and 286,000 in the Hensen, as against 160,000 in the weight net and smaller numbers in those at the surface. Other cases may not be so striking as this one, but still it is true of many hauls that the Nansen net, especially, brought a large number of Diatoms from the lower zone of water. In eases where, as on Form 71, p. 201, the Hensen and Nansen nets have yielded smaller numbers, say, of Copepoda than the weighted and surface nets no conclu- sions can be drawn, as it must always be remembered that the open tow-nets have sampled very much larger volumes of water than have passed through the vertical nets. Form 21, p. 209, shows a case where the Nansen net, as usual, has caught much more than the Hensen, but where it has not caught more than the average of the three open tow-nets in the water above, but still when the constitution of the catch is analysed it is noted that most of the Diatoms are in the Nansen and Hensen nets, and that the greater bulk of the catches from the upper layers of water is made up of Copepoda and other larger organisms. It is rare for the Hensen net to catch more than the Nansen, but an example of thai is seen on Form 45, p. 218. The shght difference in bulk (0 c.c.) 1s, however, probably due in this case to the presence of a few Copepoda, Medusae and Oikopleura, and is thus of an accidental or non-significant nature. Form 41 on p. 221 shows what we consider to be a fairly representative series 4 ‘ 4 SEA-FISHERIES LABORATORY. 233 of catches on an off-shore station, the Nansen being ereater than the Hensen and the three open nets being ereater still, while the weight net has caught more again than those on the surface. Form 42 on the second off-shore station at the same date shows a very similar proportion between the catches. Many other similar examples might be given. On the other hand, there are eases, such as station IIT on April 4th, when the Hensen and Nansen brought up such enormous quantities of Diatoms from the lower zone of water as to outnumber many times over the catch of all the other nets put together. On this occasion, the Hensen nets caught 64°5 c.c. and the Nansen 164 ¢.c., and several numbers of individual species of Diatoms in a single net run into millions, Chaetoceros contortum being estimated at fifteen millions in the Nansen net. On the following day at the second off-shore station the number of that Diatom is estimated at fourteen millions and the total amount in the Nansen net was 100 c.c., while the Hensen had only 125c.c. The surface nets were 9 and 12 respectively, and the weighted net 15°5 c.c. Although the numbers are not so high in the case of other groups, the same general principle holds later in April, when the Diatoms are disappearing and the Copepods are more abundant. We find that the Nansen net still obtains a much larger catch, and that the bulk of it is then made up of adult and larval Copepoda. For example, on April 22nd, at off-shore station I, the Nansen catch was 6c¢.c. and the Hensen le.c. The Nansen had 2,250 Copepoda and the Hensen 185; the Nansen had 15,000 Copepod Nauplu, and the Hensen 3,000; the Nansen had 1,500 later Copepod larvae, and the Hensen had 250; the Nansen had 1,000 Oikopleura, and the Hensen 125. Many other similar examples might be given, 234 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. One of our objects throughout this work was to sample the various layers of water, as well as to compare neighbouring localities and adjoining dates, and the following diagrammatic statement of certain of the hauls taken on September 12th will illustrate that part of the plan of the work : — Surface Sh.2. Fic. 5.—Diagram to show the hauls taken at one station. I.—VI. represent hauls of the vertical closing nets; W.n. (weight net), Sh. 1 and Sh. 2 (shear net) and the two surface nets represent horizontal or oblique hauls. The numbers 5 to 60 indicate depths in fathoms. SEA-FISHERIES LABORATORY. 235 Here, out in the middle of the channel between Ireland and the Isle of Man, the depth was about 65 fathoms, and we sank our vertical nets down to 60, and hauled them up through the lower ten fathoms (I), the lower thirty (II), and the entire depth (IIT), then through the zones 30 to 20 (IV), twenty to ten (V), and ten to five (VI). That brought us in touch with the surface zone through which the weight-net, the shear-nets and the surface-nets had ranged. In this way we hoped to be able to localise the constituents of the fauna obtained in a vertical haul such as IIT. It is clear that much further work in this direction is needed. Some of these serial hauls support the idea that there is a definite zone beneath the surface holding the maximum of organisms; but other hauls again seem to give contradictory evidence. For example, in the Hensen net hauls represented in the diagram (fig. 5) dealing with September 12th, Hensen I and Hensen IT and Hensen IV all contained very small quantities of _ material, 0°1 c.c., each, while Hensen VI contained a very little more, 0°15 c.c. Hensen IIT, open all the way from the bottom to the surface, contained distinctly more material, 0°25 c.c., and Hensen VI drawn through a narrow zone of five fathoms only (ten to five fathoms) contained as much as Hensen III, indicating that most of the organisms were on this occasion contained in this narrow zone between five and ten fathoms. The Nansen hauls, on the other hand, did not bear this out, No. II and No. V containing more than either III or VI. We feel that we have not yet sufficient data as to these serial vertical hauls to make it possible to discuss the matter of zonal distribution further at present, 236 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. DISCUSSION OF THE GROUPS. Turning now to the details of the various groups of organisms in the different hauls throughout the year we have, first of all, taken out the numbers of these groups from the lists day by day, dividing the totals by the number of hauls of the nets made on that day, so as to get results for each group, per day, per net. We have treated in that way the Diatoms, the Dinoflagellates, the Copepoda, the Cladocera, and a few of the more prominent single species such as Ceratiwm tripos, Sagitta bipunctata, Tomo pteris onisciformis, Otkopleura diowca, and some of the Copepoda. | DIATOMS. The variation in the total catch of Diatoms throughout the year will be seen from the following list. All the days upon which plankton gatherings were taken are recorded, and the Diatoms from all nets on each day are added together, the average per net for that day being given in the last column. Nets. Total. Average per net. Jan. 8 1 = ' 5,650 ar. 5,650 18 1 = 34,300 a 34,300 Feb. 5 = 152,600 sat 152,600 22 t= 205,050 “es 205,050 26 4 = 293,900 are 73,475 Mar. 4 3 = 284,000 ae 94,666 26 2 220/000 a 110,000 27 1 =) ) (2773000 ese 277,000 29 1 = 326,000 } 29 tees 180,650 ; OL en Apr. 1 5 = 425,000) 1 3 593000 f 118,500 2 4 = 1,000,000 a 250,000 3 i Rae or 335,000 4 4 = 890,000 4 5 20;434, 0000 a mee 5 5 = 17,669,000 ie 3,533,800 6 2= 697,500 xs 348,750 8 5 = 12,362,000 ) 9 8 be= cACe CON a ai Le 9 5 = 1,249,000 9 5\= 696,000 9 9 oe = 159,000 oa iat 9 2 = 702,000 SEA-FISHERIES LABORATORY. R Nets Total. Average per nev. Apr. 10 2= 247,000 ° 10 5 = 3,662,000 10 a 324,000 297,706 10 a 414,000 19 2 = 414,000 11 5 = 2,533,000 ) 1 3) tt 514,000) | ge0,878 13 5 = 2,269,000 13 a 162,000 13 5 = ie aaa 13 2 se 232,000 15 a oo 15 5 = 528,000 93,727 15 1 = 184,000 } 16 a 352,000 16 6 = 107,000 16 pe ze. 44,600 16 l= 122,000 17 i 215,000 215,000 18 on 371,000 18 5 = 377,000 18 a 9,000 eoee 18 i 73,000 19 a 300,000 19 a 458,000 oh 74,455 19 1 = 61,000 ; 22, 5 = 1,700 22 5 = 1,400 600 22 i 3,500 2a — 1,500 23 5 = 4,300 1,342 23 = 1,300 7a 1 = 9,000 24 4 = 2,663,000 es os 1,452 | 191,873 24 5 = 211,000 ( 24 l= 2,650 | 25 — 6,200 25 5 = 3 663 75, a 1,500 25 1 = 1,350 26 6 = 200,000 26 5 = a0 | 16,982 26 1 = 250 21 5 = 64,000 21 6 = 51,000 27 5 = 202,000 16,890 ah 5 = 6,770 74g | 1 = 47,800 May 8 SS 238,650 238,650 18 1 = 15,250 15,250 24 1 = 39,650 39,650 June 11 = 103,000 103,000 15 1 = 8,500 8,500 21 ie 6,075 6,075 July 5 i 61,475 61,475 12 —— 47,450 47,450 17 tS 44450 44.450 31 A 1 = 50 50 Aug. 9 to 20.—No Diatoms 74) | eee Gn = 25 6 21 5 = 40 a -.NSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Nets Total. Average per net. Aug. 23 3 = 4 | 23 a Bois. °c 8 23 — 30 } 24 3 = 70 24 pS 340 24 Aj = 6,060 [ ~" = 24 "pee 1,600 26 6)'= 580 | 57 26 gl = 105 j 27 3) = 400 133 28 a = 3,270 ) 28 Ss 1,480 | oo 29 3 4,055 811 30 1S 250 250 31 12 = 2,610 217 Sept. 2 6 = 460 76 3 3) = 2,475 3 S= 5,485 ee 4 7 = 3,000 4 5 = 4,528 B75 4, 5 = 3,400 6 9 = 2,600 6 Or = oa | 390 6 = 1,445 9 3 = 28,400 9,467 10 T= 6,340 906 11 c= 3,900 ) 11 8 = 4,925 743 11 S = 9,000 12 8 = 29,960,000 12 8 = 7.00 | 1,843,684 12 3 = 5,000,000 13 3 = DIORO) Ie 993 14 Dv 1.6005 | ox 1,600 16 T= 5,658 fe. 808 17 i 55,000 17 7 = sara oo Qe: 18 T= PTT 18 e = 16,000 ; 7" ae 19 Sa 12,317 a 1,539 20 9 — 4,245,000 20 D = 88,000 20 9 = 558,000f °° 477,664 20 5 = 10,394,250 2] i) = 8.000) aa 8,000 23 l= 1550s ee 11,550 24 in 31,950. 31,950 26 k= 108,655 - o. 108,655 Dy I= 128,350 «..: 128,350 28 1 =, 5 4156,150: ) = 156,150 30 Y =e ned 70250 me 579,250 Oct. 1 l= 91,050 —s«.... 91,050 9 i SAO) Bae 2,450 14 | ss 0: (ne 0 24 i= 3 (0) rere 3,500 Nov. 4 pS 6-530) beets 6,530 8 I =» > 159,300: pos) 159,300 16 | = 26,685 ... 26,685 25 1 75.075. to) 75,075 Nec. 12 — 13890) «Abs 13,820 200 — LL ARO. We 11,450 28 1 = 6.950 @ a 6,950 30 iS 8,000... 8,000 SEA-FISHERIES LABORATORY. 239 From these daily averages a three-days’ average has now been made, with results as follows :— Daily 3-daily Daily 3-daily Nets Average Average Nets Average Average 2. Mar. 26— 110,000 — 12. Aug. 26— 57 205 LZ 27— 277,000 162,777 | 3. 27— 133 176 5. 29— 101,330 165,610 | 14. 28— 339 428 8. April 1— 118,500 156,610] 5. 29— 811. 467 4, 2— 250,000 234,500 | 1. 30— 250 426 1 3— 335,000 738,583 | 12. 31— 217 18] 9 4— 2,369,333 2,079,378 | 6. Sept. 2— 76 339 5. 5— 3,533,800 2,083,961 | LI. 3— 724 458 2. 6— 348,750 1,867,717 | 19. 4—. 575 563 10. 8— 1,720,600 756,593 | 27. 6— 390 3,477 14. 9— 200,429 739,578 | 3. 9—. 9,467 3,588 17. 10— 297,706 326,345 | 7. 10— 906 3,705 8. 11— 380,900 294,491 | 24. 11— 743 = 615,111 15. 13— 204,867 226,498 | 19. 12— 1,843,684 615,140 iH. 15— 93,727 114,398 | 3. 13— 993 615,426 15. 16— 44,600 114,442] 1. 14— 1,600 1,134 b. 17— 215,000 106,295 | 7. 16— 808 2,707 14. 18— 59,286 116,247 | 14. 17— 5,714 2,591 Ff. 19— 74,455 44,780 | 15. 18— 1,252 2,835 Lk 22— 600 25,466 | 8. 19— ~- 1,539 160,152 12. 23— 1,342 64,605 | 32. 20— 477,664 162,401 15. 24— =191,873 64,626 | 1. 21— 8,000 165,738 15. 25— 663 69,839 | 1. 23— 11,550 17,167 12. 26— _——:16, 982 Piola) 1 24— = 31,950 49,052 22. 27— 16,890 — IE 26— 103,655 88,652 Aug. 20— — Z|) 1. 27— 130,350 120,785 11. 21— 6 Zag eal 28— 128,350 279,317 22— — a Ae 30— 579,250 266,217 12. 23— 8 144) 1. Oct. 1— ~~ 91,050 — 19: 24— 425 163 | On considering this list, the following points come out:—The average number of Diatoms per catch often varies considerably from day to day, as will be seen by a glance at the table. Thus on April 5th the average of all catches of that day was 3,533,800, while on April 6th it fell to 348,750; on April 24th it was 191,873, while on April 25th it was only 663. Again, on September 10th and 11th it was 906 and 743 respectively, but rose to 1,845,684 on the following day; on September 19th it was 1,539, while on September 20th it was 477,664. Each of the above numbers, however, is the average of several catches, that is of all the nettings taken during 240 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. a single day, and they do not by any means give an adequate idea of the quantitative variation among individual catches. Thus on September 10th surface nets I and II contained 250 and 550 respectively, while two days later the corresponding numbers were 13,495,500 and 16,300,500; on April 8th two hauls of the Nansen net gave respectively 198,000 and 3,739,000, and many other such cases could be quoted. Such differences as above cited are due in the main to the great abundance of some single organism, generally Rhizosolenia semispina, Chaetoceros contortum, C. debile or Thalassiosira nordenskioldti. Thus of the two enormous surface nettings of September 12th given above, Rhizosolema semispina accounts for thirteen millions and sixteen millions of the organisms respectively ; again the high average (477,664) of 32 hauls made on September 20th is traceable largely to the influence of four of the catches amounting together to 13,230,150, of which 15,085,000 were Rhezosolenia semispina. Besides, however, these great fluctuating changes it will be seen that there is a more regular seasonal change. This is brought out more clearly by the diagram (p. 269). Owing to the frequency of the spring and autumn hauls it is possible to take 3-daily averages from March 27th to April 26th, and again from August 20th to September 30th, but it should be noted that while the spring catches and those of the middle (August 23rd to September 19th) of the autumn period were made with several kinds of nets outside the Bay, together with surface nets within the Bay, those on other occasions were made only by the surface nets within the Bay; at other times than the above two periods the nettings numbered from three to four per month. The curve shows two humps, a well-marked one in SEA-FISHERIES LABORATORY. QAI early April and a less conspicuous one during the latter half of September. The spring hump rises suddenly and falls again almost as suddenly, the main portion occupying about three weeks (the last week in March and the first fortnight in April). It is to be noted that its height is largely influenced by the catches of three days, namely, April 4th (2,369,333), April dth (3,533,800) and April 8th (1,720,600), which were due mainly to the large numbers of Chaetoceros contortum, C. debile and Thalassiosira nordenskioldit in certain of the nettings included. Omitting these three days, however, the curve retains the same general character as before, except that the peak is very materially reduced. | The autumn hump is not so well marked, in fact if the catches of the three days, September 12th, 20th and 30th, be omitted it almost entirely disappears and 1s confined to the last week in September; it depends, moreover, entirely upon surface nettings taken in the Bay. At other times of the year the catches were small, reaching, however, about 200,000 now and then sporadi- cally. The minima were during August, October and December, in particular from August 9th to August 20th, when no Diatoms were taken, though surface nettings were made (within the Bay) on all the days with two exceptions. DINOFLAGELLATA. The following list of the Dinoflagellata throughout the year is drawn up on exactly the same lines as that for the Diatoms. Nets. Total. Average per Net. Jan. 8 ES 0 es 0 18 LS 100 wa 100 Feb. 5 | Ge 1,400 ae 1,400 249, TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. May June July Aug. Nets. —_— YO OU — —_ — i DOK or WHO Or NPT ST ST TW SST I TE SW UST SPSS USS SSIS Ve Mey St at Th ALE TEI TIE SITE USS STS SSS SSeS Total. 750 300 0 4,000 7,900 14,900 3,500 5,700 16,500 3,600 30,050 79,850 84,350 12,500 29,350 36,450 31,245 4,500 38,125 43,700 7,895 11,100 49,259 14,248 39,735 32,255 3,575 1,850 3,000 5,000 375 3,000 2,575 3,375 8,000 3,750 0 1,000 2,000 2,000 1,000 1,000 900 112 787 1,582 8,201 875 3,244 5,250 1,190 1,735 9,095 5,665 300 3,605 Average per Net. 750 75 0 2,000 1,580 1,862 875 3,300 1,800 3,005 5,704 4,962 1,562 1,957 3,313 2,083 4,500 2,723 3,972 yi hye 925 3,284 950 2,838 1,792 3,575 1,850 3,000 5,000 375 3,000 2,575 3,375 8,000 3,750 0 1,000 2,000 2,000 1,000 1,000 500 SEA-FISHERIES LABORATORY. 243 Nets. Total. Average per net. Sept. 2 Ge 2,235 372 3 1 eee 16,611 1,510 4 Ue 6,305 332 5 b= 50 50 6 26° = 11,356 436 9 3 = 10,900 3,633 10 i = 2,950 oat 421 i! 24 = 19,876 S25 828 12 eh = 195,835 Rs 10,307 13 a 2,750 oe 917 14 bs 1,700 a 1,700 16 8. = 4,635 eee 579 17 1 22,49] oe 1,606 18 1a 4,427 i 295 19 Wee 6,820 aor 758 20 36 = 44,502 a 1,236 21 l= 1,000 oi 1,000 23 t= 750 ster 750 24 | ieee 1,750 a 1,750 26 | ge 1,000 Sas 1,000 27 LS 2,250 oan 2,250 28 Ree 1,500 se 1,500 30 wile es 1,500 ate 1,500 Oct. 1) a 4 0 0 14) 1 24 | Nov. 4 | ge 225 225 8 = 200 200 16 lL = 600 600 25 lez 1,125 e: 1,125 Dee, | 470 wicks 470) 20 t= 650 ae 650 23 te 300 e 300 30 | ire 600 ais 600 From the above list of the Dinoflagellate catches, and the accompanying curve (compiled from a total of . 695 hauls), it is seen that the numbers rise from a very low point at the beginning of the year to a series of peaks in April, the highest of which is 5,704 per haul on the 9th, and in July a higher point (8,000) is reached, after which the numbers fall and keep generally at a lower level until the middle of September, when for a single day a very high average is attained, 10,307, the highest in the year. After this there is a very rapid fall, the 244 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. group is unrepresented in October,* and the numbers keep irregular but low during November, December and January. We have taken out separately from the statistics the figures in regard to Ceratium tripos, perhaps the most abundant species of Dinoflagellate in our district. It is Bago Suue0uec Soe Dt =e GRRE Teele ee aes Sees aeonusno — ee = Bo aopol i | TT tt ttt yy DBUGRHEREESGeBHoa DOL aesuue! SSSR 0RCRRER000HR0808 E2ULESeeSSesooeesaeae seeee Beaae aa Oo -— — 1 ! ‘Set ae sa or an eae = — oe ] 268 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 32, 36.—Port Hrin Bay, April 16th. April 17th. Net used aii Baidecd mtecsenaeds LA VG L.A Le Depth in fathoms ............ 0 i) 0 0 Wate vim ClCmn” fc: secon eases 20 16 26 25 Biddulphia mobiliensis ...... 36,000 40,000 57,000 85,000 Chaetoceros contortum ...... 3,000 1,000 8,000 6,000 a decipiens fhe se. — — 5,000 5.000 Coscinodiscus concinnus ...... 17,000 23,000 22,000 20,000 Rhizosolenia semispina ...... 500 — 1,000 — on shrubsolei ...... — — 2,000 ; — Thalassiosira nordenskioldii 1,000 1,000 2,000 2,000 Lauderia borealis «.............. ~- -— — 500 Ceratimmrfusiis A. .nse. sense — 500 500 — Pe ELMOOS * yeinnies wdeeoce ne — 1,000 — 3,000 Peridiniuimispsce-eescsee se 1,500 2,000 — 1,000 Medusoid gonophores ......... 3 3 64 92 Sagitta bipunctata ............ 10 10 30 15 Marval’ Polychaeta, aavere.. + 300 300 2,100 920 os (Natives, 77 0b sec ctecpoes ete eters we -— a 500 = Crab Zoea: Sea cjce as clbte anes 2 5 ] 1 Mysis stage of Crangon ...... — — 2 2 Nephrops, Ist stage ............ — — 1 1 Calanus helgolandicus ......... 150 50 - 240 130 Pseudocalanus elongatus ... 800 350 1,800 980 Vemora longicornmis <...:....... 4,600 2,800 6,000 4,400 Centropages hamatus ......... 100 a 00 16 8 PNCATLIA) ClAUSiey sce). aac 1,250 800 625 720 Oithona tsimlisiie ss. 4--sesaae ees 250 100 210 530 Anomaloceral qUy. «...0..:s08>:-: 50 50 — — Copepod tra npliin tees e 6,000 11,500 40,000 25,000 5 IULVARN Sensis. sc ceamanenaas 10,000 12.000 15,000 16,000 Barnacle manipliit. t..c-hace-on. 1,000 350 2,100 920 ss cypris stage ......... 200 200 80 80 Oikopletral ss a.ccesasceeeeee 2,250 2,250 2,850 2.400 Fish eggs— Rocleling am cess oe dese eines — 4 _ — Common Dragonet ...... 2 3 ] _- Loy Osh Bo bne nee nme Mineciaet ce 1 2 — ] Pople Osea wctot cintectemetetele ] 3 —— — SPhats cee skhs odecteeceesee ster -= ] — 2 Dalb* Gaseseaticcaseotetetnes ~- — — ] Young fishes— Clupeoid's 6h. cence 2 —- — 1 GAGOIGN Se scwseniss sottts cans — — 1 2 both Diatoms and Copepoda had increased considerably (see Forms 32, 36). Copepod Naupli, however, seem to rise and fall in yi number on the same dates as the Diatoms; but on the SEA-FISHERIES LABORATORY. 269 whole the Copepod Nauplii increase to a maximum on April 17th, when they are exceptionally numerous (see Form 36), and then fall off, so that the numbers at the end of the month are much the same as those at the beginning of the period under observation. | Tt is clear then that the problem of the periodic distribution of these various organisms is not quite sc simple as might have been expected. There are probably three distinct factors at work :—-(1) the periodicity of the stages in the normal life-history of the organism; (2) irregularities imtroduced by the inter-action of tha 2 205g be E CAee SES Me meee pacer} [ok I Le eT dee Td ee oye Sanaa Speuaes organisms, as when one group serves as food, or enemy of another: and (3) abnormalities as to either time or abundance caused by weather conditions, which may either prevent the normal or permit of an abnormal development of certain species. Mr. Laurie has kindly drawn for us the accom- panying curve (fig. 9) representing our results as to the Diatoms in the bay compared with those from the open sea. 270 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. It will be noted that the general character of the curves is similar, though the catch in the bay is consistently greater than that at sea. The less sudden diminution in the number of Diatoms in the bay from April 10th to April 17th will be observed, and the sudden drop which then follows, bringing the curves close together by the 25rd of the month. The numbers of the total Diatoms from the hauls in the open sea during a month in spring are as follows :— Average 3-day Date. Hauls. per haul. average.* Mar. 29 + 45,162 ay — April 1 3 103,333 mA 111,998 2 2 187,500 vai 209.055 4 4 336,333 sie 198,722 5 2 72,333 qo 230,111 8 3 281,667 aes 142,133 9 5 72,400 ae 136,133 10 6 54,333 el 56,578 i] + 43,000 sea 44,175 13 6 35,192 ai 32,811 15 4 20,240 sie 23,465 16 8 14,962 Ne 16,651 18 4 14,750 fee 13,237 19 + 10,000 Hae 8,349 22 + 297 ae 3.746» 23 6 942 ie 551 24 4 415 bit 661 25 6 625 — 1,780 26 + 4,300 tin 3.880 27 7 6,714 se — * By ‘‘ three-day averages”? is meant taking always the average of the three adjacent days upon which catches were made, 7.e¢., the average of the Ist, 2nd and 3rd, then of the 2nd, 3rd and 4th, then of the 3rd, 4th and 5th; and so on. Bay DIATOMS THROUGHOUT THE YEAR. A general inspection of the unsmoothed curve shows a well-marked maximum at the end of March and earlier part of April. The marked increase of Diatoms, and also of Copepod nauplu, towards the end of March is seen well in the surface hauls taken in Port Erin Bay on the following three dates :— SEA-FISHERIES LABORATORY DEA March 26. March 27. March 29. 12 c.c. 14°5 c.c. Sco) crc: Total Diatoms = 220,000 ... PTA V UC ar 326,000 Biddulphia mobiliensis......... 46,000... 50,000... 58,000 Chaetoceros debile ............ 6,000... 8,000... 10,000 gis decipiens’ ..... .22%: 100,000... 150,000... 160,000 Coscinodiscus concinnus ...... 64,000... 67,000 ... 75,000 Sonepod nauplit— 22... cers 7,000... 27,000 ... 35,000 We have only quoted those species of Diatoms which are present in greatest abundance and which make up the bulk of the catch. All are included in the totals given. There is also an autumn maximum showing a very high peak at the end of September. Omitting, however, the single catch of September 30th (which is due in the main to Rhizosolenia semispina) the peak is reduced to less than one-third its former height. A remarkable feature of this September hump is the sudden character of its appearance and disappearance and its short duration (six days). An inspection of the temperature curve of the year for the water of the bay (fig. 10) shows that the sudden increase = ee. Ch JOCK De Roo Sooo DNoeeao jseusce seas BOR Sos=000 in the phytoplankton coincided with the maximum in temperature, and our weekly weather records at the Biological Station show at that same time a week of fine calm weather with easterly breezes (S.H. and H.S.E.). We have noticed the same phenomenon in previous vears, both at Port Erin and on the west coast of Scotland, which seems to indicate that if weather conditions be suitable at 272 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY, 122, 123.—-Port Erin Bay, October Ist and 14th, November 8th. Surface. Oct. 1 Oct. 14 Nov. 8 Depth inathomis Ah coaedecaelasitcrieseris sacs 0 0 0 Wateh inn Cxemis Weve aasielaclelae -leeeenes seer 1°5 11°5 6 Biddulphia miro biliensis:;j.-.s-cecneeecuess eset 500 -~ 5,600 Chaetocerostcontortumil <5. aeeacees 2,750 — 300 3 Gebile: (hcseseteeusctecasone ene 500 — -- re GeCciPleMS sesseene ene veeene een 3,500 — 3,000 i BOCIALE aacisenes domacieneten eee iaes 3,250 — 400 i GELS | Aeaa cosine cease ence ae ceemeee 2,000 — 146,000 fs GenswiM: Be Siteecdecc ene 3,250 _- 400 4 Dorealee sos tectece cates eens 750 — = “ Sulbtile yc orcas cect -co-eeiecic 250 —- — ~ CEVELSUIN ia. ccna eeees 750 — — Goscinodiscus (ConcimmMUBie cece eae eee. — — 1,800 Rhizosolenia S€mispina ..........c5..e00es ne 68,300 — 400 sy alaitays 7)! (Aah P keen atten eens 1,000 _— — M Shiu bSOleiiee ss seece ease 2,500 —: — DOSCIMOUISCUSITAGIALUS Umece-cpeececseee en re 500 — 1,000 HAGLCLIASEMUMMIES Py seeeeeesmemesssyaek eee eee 250 — (CUIMEN ROIS, TR@ONGIG,, A obbocdocnadconbaonnoscuns > 1,000 — 300 Streptothecar span vac cece oaciieeeeemeedas ~— —- 100 Pera Crips, sasccece ose seees eee — — 200 Meduso1d jw onopWores) ies. -ce seers reer eeep 2 3 20 Davicvaibipumebabarysccescenuescese. ceekeee 5 190 56 Tomeapteris (OMmisciOrunisit.. v1.2.2 e-eeeeene — 8 1 Marval Moly chaetayqmcnoseecaciten sce ene eee — 250 — < MGGRATIG Le si vecd dscmeataceeniac «een tateenas — 250 100 Cra gOS Vise. cccinec seons ceeeies contents cists — 10 — Mysis stagenot Crane ony s.2:- ee eeseeeaas i 20 a! Br Vib LE OOS 180.0 erasctanncectors liom iaioshene eres acat — —- — Mieroniseusscalamia....cceecce- cesses —— 50 — Calanus heloolandictis jc. e rs -lrscctelceen el — 2,700 85 Pseudocalanus elongatus ...............045 220 8,100 1,350 Memona lone iC OnMIS) ec jesccsiecleesstenicleseets — 70 8 Centropages hamatus ..0.....-......cen.nonse a 150 2 Anomalocera pattersoni ...............0+. = _ 1 NCANGa CCLAUSI! “is sais ce ctv. tee eeaclooe Meee 275 650 1,770 Orxthona:-sumilus soc sc cues nacotire aeene ener 485 12,600 6,170 Paracalanus (parvils) --resmos--riccarisewere eres 30 3,300 1,450 Microcalanus i pusillis aeeerceeeseer eee 35 — 100 Parapontellabrevacornis a... see veeeeenee — 30 — Tsiasclavipes © wm. cccrteacens 15 oeeneneesemnionidee — 190 1 Copepod:nauplit- oc. scnsecnees tn aecomaneener 2,500 5,500 3,200 oe fUVic su noeatessineee epee canciuacemane: 500 23,000 4,500 Gasteropods, lanvallecn.ctata-resneseee saree er 250 — 300 amelhibranche, larval ee osn-eeeestsaeeeeeeete — 1,250 300 Oikopleutra Sp: > 7itvnbo scence 50 725 575 SEA-FISHERIES LABORATORY. O78 the end of autumn the phytoplankton may suddenly increase so as to constitute a second maximum in the year, the first being in spring; but that this possible maximum may be so modified in time and in amount by temperature and wind as to be unrecognisable. In 1906 it was very much more marked at Port Erin (see XXth Ann. Report, p. 53) than in 1907, and extended from September 20th to the end of the month. The phytoplankton minimum for the bay occurs in August, no Diatoms being taken from August 9th to August 23rd (see curve), though nettings were taken on all days, except three, included between these dates. As an example of a sudden change in the plankton we may compare the surface hauls taken in the bay on October 1st and 14th (see Form 122). The total quantities of the two gatherings were 1°5 and 11°65 respectively; on the Ist, Diatoms were relatively abundant (over 91,000) ; by the 14th they had disappeared. But Sagitta and various larvae, and especially Copepoda, had greatly increased in number by the latter date. The adult Copepoda in all numbered only 1,045 on the Ist, while they reached 27,790 by the 14th; younger forms and Naupli had also become much more abundant. By November, however, the Diatoms were back in quantity, as 1s shown by the third column (November 8th), and Copepoda have begun to decrease again. Bay CoPpEPODA THROUGHOUT THE YEAR. Copepoda are fairly abundant in Port Erin Bay from April to November inclusive, but there are considerable ups and downs, the number per haul varying often on successive days within very wide limits. The curve (fig. 11) shows a gradual increase from the latter part of March through April, then (with depressions 274 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. in the beginning of May and the end of August) there are successive humps in June, early August and September leading to the maximum in October. This is followed by a rapid fall in November, and the minimum extends through December, January and February, the numbers commencing to rise again in March. On comparing the two curves it will be noticed that the April maximum for Copepoda is distinctly later than that for Diatoms, and that again the October maximum for Copepoda follows after the September increase of Diatoms. To a less extent throughout the rest of the year the two curves are complementary with the exception of late August and early September, when both are low. ~ ew Luey wed 5 [Spj0p® | [ | T | SESEHES SGlseeeas | tI SUseereceegare7seeearet FH PEE [| 4 ne ae (lTatats lair | Adierste| Sa BESa fo eHee : Stace a EEEEEEH rH Sores seeaeeeeeceeseretes HEHE siegesinies SEESEoussaseesseecesacesseeeseasserasseeeeertze HEEL 1, JOO SSSheeao Sagnesesaneee Gaon gaeee ppt aid BEEEEEEEEEEEEE EEE EEE EEE EEE EERE S58 ~ 4h | (DER SE BS WS SS eeoooses SASH PEC M4 EEE REE EEE BBS BEHSsoea CN [TT htt vy [| AT | Prati Hot BEaa 1s bee bt Ay AE iO A Tt | 4 ESP LSSSeSe5 CEETEEEEEEEE EEF EEE-EPe EEE EEE ct Af ee PEEeEH U SEEEGGT GUS UGES Ver eee] ideo (et uaeEeAbEPEGE T | NSSESRD4BSSERSEModa igs ny HEL PACKS Tt 7" A My rity | LG S18 Sw Be, \ [osetia Ws [| NK | AT H+ 4 \ = ines HEEL HH NE ee seed , EEE EEE EHR aoe VIROL YAGI BLAFH Is SG NWA as ra ay \ Tay Tae Fat Supt = Ot = jae Dec CIRRIPEDE LARVAE IN Bay. The Nauplius and Cypris stages of Balanus form an interesting study. The adult Balani are present in enormous abundance on the rocks of Bradda Head, and they reproduce in winter, at the beginning of the year. The Nauplii first appeared-in 1907 in the bay gatherings on February 22nd, and increased with ups and downs to their maximum on April 15th, and then decreased until = SEA-FISHERIES LABORATORY. 275 their disappearance on April 26th. None were taken at any other time of the year. The “ Cypris” stage follows on after the Nauplius. It is first taken in the bay on April 6th, rises to its maximum on the same day with the Nauplii, and was last caught on May 24th. Figure 12 He Hl I at | Pee BERR EREE a DEGREE aeo Bbeod [1 i TTT TT TTT Yt | aeeee | eS SE SHaR RSE SSSR eane SS Soe S Pees Saehesapz SRRESSR eS SEUSAREP A aebol tT rrr rt arr BSRRS 2 SR EeeEsZ aes Serene ssa Atala) [| + +4 V1 | Saag a Pasee.en PSC CCC Sb Sines iellelids Se Ab ae Sepdeec Cec Emacs eer 9 oA = epee aie es Fel Mar apt May Tee ss shows the curves for these two successive larval stages. It will be noticed how the “ Cypris”’ curve keeps below that of the Nauplius, the maxima being 1,740 and 10,500 respectively. Probably the difference between the two curves represents the death-rate of the Balani during the Nauplhus stage. SAGITTA IN Bay. - The numbers of Sagitta brpunctata obtained in the bay catches throughout the year run as follows per haul: =a mew. = Mare ty Apr; 8, 7, 24, to, 20, 40, ae, ot, 69. 20, 5, 4; May, 6, 100, 20; June, 95, 30, 15; July, 3, 35, 40, 425; Aug., 75, 100, 1,000, 200, 600, 1,800, 800, 700, 8, 54, 65, 63, 76; Sept., 16, 10, 40, 20, 20, 3, go, 10, 50, 100, 10, 32, 50, 10; Oct., 5, 10, 190, 90; Nov., 324,. 56, 1; Dec., 1, 8, 50. Fig. 13 shows the 276 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. curve drawn from these numbers, showing the more prominent humps in the height of summer and again in October-November. Sagitta is present throughout the year; it is most abundant in August, and the minimum occurs in winter (January to March). We have not yet made a curve for the occurrence of Sagitta outside the bay, but so far as an inspection of the numbers shows the result would not differ materially from that given above. Those nets that are comparable give much the same run of numbers. As showing, however, the difference produced by a larger net of wider Poo os mrt tb cH EEE saanett sateeeas ECE Nel Sora SEO0o PR CRS rT] 264 Day Cott = 2 3/4 mesh, we find that during April, when the hauls with the ordinary tow-nets were giving units and tens, those taken at the same time with the shear-net ran into hundreds, as follows :—360, 123, 286, 310, 200, 200, 400, 400, 300, 500, 60. The fact, however, that the weighted tow-net, not invariably, but usually took a much larger number than the similar surface nets shows that Sagitta is usually more abundant in a zone of water below the surface, extending down to ten fathoms, and that consequently the SEA-FISHERIES LABORATORY. Oe much greater numbers obtained by the shear net may be due not wholly to the size of the net and mesh but in part to the depth at which it was worked. We give the following lst as examples to show the difference in numbers of Sagitta caught by the surface (0 fathoms) and the weighted (10 fathoms) nets : — 0 10 0 10 0 10 0 10 0 10 faths. faths. faths. faths. faths. faths. faths. faths. faths. faths. Gc -20 | pees (0) i os, 16 Oj 2? Die Ay 1 6 ee iity ot Lad: Ae re eS lopexe! 85 DAN 2s &i2..%.8 OA ERE a9 1... 200 See Ly) cs g55 ae @ 2. 24 2 FS A () bes 28 4... 240 a 2 . 10 PN eee 2 94 2 = 62 eng) a We have occasional evidence from the closing nets that Sagitta is even more abundant in deeper water still. For example, on April 9th, at Station II, the surface net took one specimen, the weighted net at ten fathoms took elght, and the Nansen net, which had been worked through twenty to ten fathoms, took ten. On the other hand, we have a few cases in which Sagitta was more abundant on the surface, e.g., on September 9th, the weighted net at ten fathoms took eight, and the two surface nets took 25 and 86 respectively. As another example of the results obtained with different nets we quote the figures from September 19th, as follows:—-the surface nets took two and six, the Hensen (hauled up vertically through twenty fathoms) two, the Nansen (vertical, twenty fathoms) one, the weighted net (ranging to ten fathoms) 126, and the shear net (about ten fathoms) 1,020 specimens. OTHER LARVAL Forms in Bay. Echinoderm larvae, Molluscan larvae and the Zoéa and Megalopa stages of crabs and some other larval forms are sporadic in their occurrence. They are only caught in abundance on rare occasions, and this is of course a 278 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. result simply of the reproductive phases in the life-history and has no connection with hydrographic conditions. The adults are gregarious and spawn at much the same time, the larvae hatch out in myriads at about the same time, and may then be caught in quantities. A notable example of this is the case described in the XXIst Annual Report of the Liverpool Marine Biology Committee, p. 37, of an enormous haul of Zoéas taken on April Ist, at Station III, in a very limited area—the same net hauled a couple of minutes before having caught none. Twenty-two thousand crab Zoéas were taken by the various nets on that occasion in about seven minutes. Inside the bay the largest hauls of crab Zoéas are 200 and 300 on August 14th and 15th. They are practi- cally absent from November to March inclusive, and during the remainder of the year occur rarely, in very small numbers. “ Mitraria’’ larvae are abundant in the earlier part of the year, and then again in winter—the range being from October to the end of April, with a maximum of 1,750 per haul in February. They are only occasionally found, and in small numbers, from May to September. Polychaete larvae are more generally distributed and more abundant throughout the year. They reach a maximum in April, when the numbers per haul between April 10th and 28rd are, 260, 1,500, 2,650, 3,800, 600, 3,020, 1,530, 2,605, 700. They did not occur for some days in the middle of August, and the numbers were usually low in November, December and January, but throughout the rest of the year the general run of the figures is several hundreds per haul, occasionally reaching a thousand. | | SEA-FISHERIES LABORATORY. 279 Fise Hees in Bay. Floating fish eggs (containing embryos) begin to make their appearance early in April in the bay and remain low in number (mostly under ten per haul) up to the middle of the month. There is a sudden rise in the Rocklng eggs on April 18th (to 45 per haul), followed by a -much more marked rise on the 22nd, and the numbers remain relatively high until the 25th (reaching a maximum of 500 per haul on the 23rd), after which they fall off rapidly and remain Jow in number and occasional in occurrence throughout the summer and autumn until September. The other fish eggs in the bay follow much the same course as the Rockling eggs, appearing at the same date, remaining low for the same period, rising at the same time, though to a much less degree—the maximum being 76 per haul—and then falling off rapidly to a low level which remains through- out the summer. VERTICAL DISTRIBUTION. We have already shown above that our weighted open tow-net, ranging from about ten fathoms up to the surface during fifteen minutes, usually captured a larger quantity of plankton than the exactly similar surface nets hauled at the same time within a foot or two of the surface. This weighted net also, in most cases, caught more than Sande. Nansem + the two vertical closing nets “ Hensen ’ (which, however, are not exactly comparable in size, either with the open tow-nets or with one another, see p. 280) hauled up as a rule through the zone of water from twenty fathoms to ten and then closed. In those cases, early in April, when either the Hensen or Nansen net showed a larger catch than the weighted net, the great bulk is seen 280 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. to be due to.an excess of Diatoms in the vertical closing nets—thus showing that the protophyta are more abundant at that time in the lower layers of water. Larger organisms such as Medusae, Sagitta, Copepoda, Larvae and Fish Eggs are more abundant in the surface and the weighted nets—and more in the latter than in the former. We also find that, using similar open tow-nets, a net towed at a depth of a fathom or so catches more than one on the surface. At the time of the phyto- plankton maximum in spring it seems from the evidence of these various nets that the Diatoms are present in an increasing ratio as one descends from the surface to at least twenty fathoms; but that the Copepoda and other larger forms are most abundant in a zone within ten fathoms of, but below, the surface—probably in some cases only a fathom or two below it. For example we may quote the following particulars from Form 28, April 13th, which is not an extreme case, as the Diatom maximum is then past :— Surface nets. Weighted net. Hensen. Nansen. (10-0 f.) (20-10 f.) (20-10 £.) Total Diatoms ... 6,500 6,650 ‘11,000 96,000 290,000 Total Copepoda... 1,970 1,880 3,180 66 335 Here the Diatoms are clearly most abundant in the depths and thin upwards; while the Copepoda are more abundant above and most abundant of all a few fathoms below the surface. Many of the Forms about this date show similar results. Later on, when the Diatoms have become much less abundant, the vertical closing nets bring up very little from the lower zones of water and are surpassed by all the other nets, e.g.— Surface nets. Hensen. Nansen. Weight. April 24—Station I. ......... 20°5 15°5 05 2 16, ‘cc. 24 Station lle. ee 7 15 3 5 ITD ee 25—Station III. ...... oD 4°5 1°5 2 20 «.c. 25—Station V. ......... 8 Teo 1 20 9°5 ¢.c 26—Station V. ......... 4 4°5 0°5 0°75 8 ce PSST EHH SETEH TEE HE HES HH HEHE TH HEH HHH EHH HEH HSHETEHHHEHT ETH HHSHH HEHE EHH HH EHH EHH EET HEHEHE HEHE SHH EHH HE EHH HEHEHE EOE Ang, 2-=Station, nen tet: 3 05 2 | 7 1 SEA-FISHERIES LABORATORY. 981 The last line shows that the same general proportions hold good in the latter part of August, when the catch is composed almost wholly of Copepoda. In August some vertical hauls to the surface were made with the Hensen and Nansen nets out in deep water (60-70 fathoms), in mid-channel between the Isle of Man and Ireland, for comparison with similar hauls where the net was closed after having traversed some definite zone of water; and, as would be expected, the complete vertical hauls generally gave a larger result than the partial ones—except in a few cases where the haul was vitiated from the net apparently having gone so near bottom as to have taken in some mud stirred up by the weight. Aug. 24—Station A.—Nansen, 60-50 faths. =0°3; 60-35 faths. =0°5 cc. 24—Station B.— __,, 60-4555. —=0-27— 60-0 ie | ae 26—Station I.— a DAR esa is) 0) ee — la a rr — . ZAAO =e, = = O75 24-0 5 ae a a a a -—Hensen 24-10 =, - —0'3 24-0 (6... Sept. 3— _ a 20210- == — 0325.7 20-0 a ) SOD 55 3— =f —Nansen, 20-10 ,, =0°5; 20-0 eo ee(IS7/ ap 4Station A.— __,, 60-30 ,, =05; 60-0 aly 4—Station B.— __,, 60-30. Ors; 60-0 Oe i » ~ —Hensen, 60-30 ,, =0°4; 60-0 ye = OL Ones There were also hauls on the last date through the zone 60-50 which showed still smaller amounts, 0°05 to Ole.c. An attempt was made to discriminate more minutely between the zones on a few occasions —e.g. September 12th, in 65 fathoms. 60-50 60-30 60-0 30-20 20-10 10-5 Hensen ...... 01 Gl 0°25 01 O15 0:25 Nansen ...... 02 03 12 0°15 0:3 0:2 These and other hauls confirm the opinion we arrived at, from the use of the open horizontal tow-nets at different depths, that the most abundant zone of life is about ten fathoms, or between that and the surface—say, between ten and five fathoms. 282 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Finally, we used the ‘‘ Mill” water-bottle on several occasions to get samples from three exact depths, with the following results :— Sept. 17th— Total organisms ......... Total Diatomis i....-.-s Total Dinoflagellata ...... Total Copepoda <%...:22. Chaetoceros teres ......... . densum...... Rhizosolenia semispina stolterfothi Coscinodiscus radiatus Ceratiunm: tureaeeees eee ° RISUIS erneseresiaeee Sept. 18th— Chaetoceros teres ......... Rhizosolenia semispina - shrubsolei a eulaitan weenie a stolterfothi Coscinodiscus radiatus Total Dinoflagellata ... Pseudocalanus elongatus Total Copepoda \) :.:::.-.. Copepod nauplii ......... Sept. 20th— Chaetoceros subtile ...... Rhizosolenia semispina “ PEW © Sonoos oF shrubsolei Be stolterfothi MotaleDiatomis” Jes ess. Total Dinoflagellata ... Copepod Sauplir =.ta...2: ee eeee eoneee eeeeee eeeeve ee eere eeseee eeesee ereree ee eeee 20 faths. — Co = m— bho ONWrR eH RO oO-I NK eK DTN eE ww — — bo — Ww =—WNe OK oT 10 faths. 5 faths, 103 40 83 29 12 6 8 5 3 1 4 2 a7 16 26 Y 2 ] ik l 3 2 1 1 300 200 I 2 12 4 I 2 1 2 32 9 4 6 5 10 20 30 35 130 610 4,200 6 40 2 10 4 10 672 4,470 59 30 18 60 These results are fairly consistent, and indicate a more abundant fauna in all groups at either ten or five On the 17th the fauna was at a lower level; the ten-fathom zone had over twice as much as the others, and the twenty was a little over the five. On the 18th also the fauna at ten fathoms predominated, but that at five fathoms came easily second. On the 20th the five-fathom fauna was much the most abundant and fathoms than at twenty. the ten-fathom came next. days the centre of density was moving slowly upwards. — - These observations should be repeated and extended, It seems as if during these SEA-FISHERIES LABORATORY. 283 but so far as they go they tend to establish the conclusion stated above as to the distribution of at least some elements of the plankton in zones of depth. HORIZONTAL DISTRIBUTION. It is clear from an inspection of the Forms recording the 650 hauls now before us, that a much more detailed analysis than we can possibly give them before the publication of this Annual Report, will be necessary in order to arrive at any definite conclusions as to the relations between the results obtained horizontally at the different localities and dates. We recognise that we are far from having exhausted the information to be derived from - these records; and the horizontal distribution, along with many other details of interest which we have noticed in the course of our work, must remain for some future occasion. A mere inspection of the Forms shows in some cases close resemblances between adjacent stations (such as I and II) on the same day, or between adjacent days at the same station, and in other cases just as striking differences. How far these points of similarity and of divergence are normal and are fundamental, or how far they are due to wind, sun, and other weather conditions, or to tidal and other currents, will require detailed consideration. - We have several times been struck by the largeness of the hauls obtained, under very difficult conditions, in the strong tidal currents that race round the Calf Island. Such hauls are especially rich in Copepoda and other larger organisms of the plankton, and this observation is co-related with the well-known richness of the bottom and the httoral faunas in that same region, and agrees 984 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. with what has been recognised by naturalists for many years, that strong currents are favourable to a profuse development of animal life. A further point that has struck us in the progress of this investigation is the obvious distribution of at least some organisms in shoals. This can occasionally be seen by the eye, when, for example, shoals of large Medusae are encountered which are so abundant for a limited area that on a calm day they may cover the surface like a tessellated pavement, and assume polygonal forms from mutual pressure. On other occasions our nets have evidently encountered swarms of Copepoda, of Cirripede Nauplu, of Crab Zoéas, of worm larvae or of other organisms. One might expect such results in the case of neritic forms, which are merely stages in the life-history of some gregarious organism; but the occurrence is by no means confined to such, 1t extends in our experience to oceanic organisms on the high seas, and this sporadic distribution in swarms has not been sufficiently taken into account by some writers who have treated of the distribution of the plankton in recent years. The enormous quantities of the Diatom T'halassiosira nordenskioldu, Cleve, in our collections early in April (e.g. on April 4th 1,750,000, on April 5th 2,000,000, on April 8th 1,350,000 in single hauls) are a noteworthy feature. According to Gran (‘“‘ Nordisches Plankton,” Lief. IIT, xix, p. 16), this is a northern species found on the coasts of Northern Europe and the east coast of America. We have not met with it in the Irish Sea before. It might be argued that this was a case of a more northerly species carried down into our area by exceptional circumstances, or on the other hand the explanation may be that the Irish Sea is within the normal range of the organism, and that SEA-FISHERIES LABORATORY. 285 special conditions have permitted of a quite exceptional development this year. In the latter case, however, it is curious that, considering all the plankton investigation that has been carried on at Port Erin and off the Lancashire coast during the last 20 years, the species has hitherto escaped notice. It appears to be present only very rarely at Plymouth and elsewhere in the English Channel (Blue-book, Cd. 3837, p. 228, 236, &e.). CONCLUSIONS. We have expressed our opinions freely, both on general questions and on matters of detail, where they occurred to us in the course of writing the preceding pages, but it may be convenient to have summarised here the main conclusions at which we have arrived. 1. It is clear that many of the great seasonal variations in the plankton are not due to changes in the sea-water such as are recognised in hydrographic observations, but are caused simply by the normal sequence of stages in the life-histories of organisms throughout the year. No amount of “ hydrographic ” change in the water will determine the presence of Kchinoderm larvae at a time of year when they are not produced, nor of Crab Megalopas when they do not naturally occur. 2. Three factors, at least, seem to us to require recognition as contributing to the constitution of the plankton from day to day throughout the year : — (1) The sequence and periodicity of the stages in the normal life history of the organisms; (2) Irregularities introduced by the inter-action of the organisms, as when one group serves as the food, or enemy, of another ; 286 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. (3) Periodic changes and abnormalities of either time or abundance caused by the character of the sea- water or by weather conditions which may either determine or prevent the normal or permit of an abnormal development of certain species. The appearance of swarms of Balanoid Nauplu, followed after an interval by the “ Cypris” stage, is an example that comes under the first head. The disappearance of Diatoms when used as food by the increasing swarms of Copepoda and other Crustacea, both larval and adult, and of the Copepoda in turn when eaten by the developing post-larval fish, are changes falling under the second head. The great increase in the number of Diatoms in spring when the physical condition of the sea-water has become favourable, the enormous development of Dinoflagellates which may take place suddenly in autumn under unusual weather conditions, the almost total suppression of a group such as the Medusae in some localities in an unusually stormy summer, and the immigration of a species or a eroup of species from the open ocean or from a neighbouring sea-area as the result of variations in the hydrographic conditions, are all examples that may be classed in the third category. | Two, or all of these factors may, however, be at work together, and so the explanation of any particular change may be a very compheated problem. The increased development of a group, or the immigration of a species, may so disturb the balance of nature as to be followed by unusual changes in other groups. 3. Lists compiled from our results and curves drawn from these lists show that, as a consequence of the above factors, certain groups and certain prominent species differ from one another greatly im their relative abundance throughout the months of the year, SEA-FISHERIES LABORATORY. 287 4. Thus, the Diatoms take on an enormous develop- ment in early spring, and reach their maximum in April, then die down during the summer, and may rise again to a second but much less important and less constant maximum in autumn. It must be borne in mind, however, that the species, and to some extent the genera, that form the autumn increase (Chaetoceros subtile and species of Rhizosolenia) are quite different from those present in spring (Chaetoceros contortum and species of Thalassiosira). 5. The Dinoflagellata rise to a maximum later than *the Diatoms, and may have a second period of sudden increase in the autumn if weather conditions are favourable. 6. The Copepoda attain to their greatest develop- ment in early summer after the Diatoms have died down, and again in late autumn (October) they follow the phytoplankton. As a rule a haul rich in Copepoda has few Diatoms, and vice versdé; but the Copepoda do not, like the Diatoms, present great maxima and marked depressions. Iiven when both groups are present in the plankton we frequently find that they are in different zones; for example, in some of the April hauls in 1907 the Diatoms were markedly on the surface and the Copepoda below, while later in the year these positions were reversed. 7. The distribution of particular Copepoda (Calanus, Anomalocera, Microcalanus, Centropages, Temora, ete.) has been discussed, and for the full results we must refer to the body of this report. Calanus, Centropages and Temora are present throughout the year; Anomalocera appears in our district in spring; Mzerocalanus in late autumn 8. Similarly the conclusions arrived at in regard to the distribution of Sagitta, Tomopteris, the Cladocera. Oikopleura, Cirripede Nauplii, and various other larval 288 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. forms and fish eggs are given in the preceding pages and need not be repeated here. . J. The Irish Sea contains a surprising number of what are usually regarded as “ Oceanic’ species—not merely as occasional visitants, but as normal and continuous constituents of the plankton during a great part of the year. Amongst these may be mentioned Chaetoceros densum, Coscinodiscus radiatus, Rhizosolenia semispina, Ceratium tripos, Peridinium sp., Tomopteris onisciformis, Sagitta bipunctata, Pleurobrachia pileus, Calanus helgolandicus, Anomalocera pattersoni, Acartia elausi, Oithona similis, and Oikopleura dioica. Some of these oceanic species seem, so far as we can judge from the published records, to be more abundant and more continuously present round the Isle of Man than they are even in the western part of the English Channel. 10. We have evidence from our closing vertical nets that the zone of most abundant life is not on the surface but is generally a few fathoms below—say, usually, between 5 and 10 fathoms. Samples of water from 5, 10 and 20 fathoms obtained with the ‘ Mill” water bottle support the above statement. But this conclusion was arrived at, and could be established, quite apart from the evidence of the vertical nets, from a comparison of the results obtained by the weighted and surface open horizontal tow-nets. 11. At the time of the Diatom maximum in spring, however, our closing vertical nets showed that these Protophyta are more abundant in the deeper zones than at the surface, and increase in density downwards to at least 20 fathoms. | 12. In the case of some groups, e.g. Cladocera and Oikopleura sp., the distribution is sometimes remarkably regular, the same numbers being taken simultaneously SEA-FISHERIES LABORATORY. 239 5 by comparable nets at localities up to ten miles apart; but on the other hand even with these same groups there may, on other dates, be very diverse hauls indicating an uneven distribution. 13. Some species, and some groups of neritic larvae markedly congregate in shoals, and this also adds to the unevenness: of the distribution. 14. The horizontal distribution of the plankton 1s consequently liable to be very variable and irregular, and although its characteristic constitution at different times of the year may be described, it is very doubtful whether any numerical estimates can be framed which will be applicable to wide areas. 15. It is clear that samples taken quarterly, monthly or even fortnightly are quite inadequate to convey a correct idea of the constitution and changes of the plankton of a sea-area in any detail; and, conse- quently, conclusions ought not to be drawn from such insufficient observations. 16. Our samples, taken weekly throughout the year, and almost daily during the three most critical months, give by no means too much information, but will probably suffice to enable us to make that detailed comparison between adjacent localities and dates which we hope to publish in the next Report with a view of determining the representative value of such periodic samples. Be ie Ween en md cal? > Pts 291 L.M.B.Cc. MEMOIRS No: XVEY CANCER. (THe EpIsLE Cras.) BY JOSEPH PEARSON, M.Sc., Demonstrator in Zoology, University of Liverpool. CONTENTS. PAGE PAGE Introduction. ... . . 292 Blood Vascular System . . 400 External Characters . . . 296 Respiratory System . . . 416 Appendases 2. < . . 312 Exeretory System. . . . 426 Endophragmal System. . 321 Nervous System . . . . 439 Structure of Integument . 335 Sense Organs . . . . . 446 legos et el) 2 4) 2) BAB Reproductive System. . . 453 Appovuemy is. B46 Development-S92))..i 5 . \.. 409 Muscular System . . . . 355 Economics and Bionomics :— Coelom and Body Cavity . 374 General Habits . . . . 468 Alimentary Canal :— The Crab Fisheries. . . 467 General Description and Size of Crabs at Maturity 467 Histology . . . . . 375 Distribution and Digestive Gland. . . . 382 Whisratiow 62.3 3S, 2 469 Ossicles of Fore-gut . . 387 Bionomics of Ecdysis. . 473 Muscles of Fore-gut . . 393 Description of Plates. . . 485 292, TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. INTRODUCTION. CANCER is a genus which has a world-wide distribution. Only one species, however, is found in Kurope, viz., Cancer pagurus, the subject of the present memoir.* This species is found on almost every part of the coasts of Europe from Norway to Greece, and it is particularly abundant on the shores of North-West Hurope (France, Germany and the British Isles). Cancer pagurus, the edible crab, has been chosen as the subject of the present memoir partly on account of its economic importance, and also because, as a type for dissection, it is easily procurable and is of a convenient size. The account given below, however, may be applied with very few alterations to any of the brachyurous Decapod Crustaceans, such as the common shore crab (Carcinus) or the swimming crab (Portunus). The edible crab is found in great abundance on the coasts of the British Isles, especially on those parts which are rocky, and gives rise to an important fishing industry. The large crabs live in fairly deep water, but the young representatives of this species may be readily obtained between tide-marks. Cancer 1s mainly carnivorous in its habits and feeding. It is particularly fond of dead fish, and it probably also feeds on other Crustaceans in a smal] degree. There is, however, no evidence to show that it has cannibalistic instincts. (For further particulars with regard to habits, distribution, crab fishery, &c., see section on EKeonomics.) Cancer pagurus was first named by Linneus, who established both the genus and the species. In his *The investigation has been dace by a grant of £25 from the Board of Agriculture and Fisheries, and the expense of producing the lithographed plates has been met in part by a grant of £30 from the ‘¢ Treasury Grant for Research ”’ of the University ‘of Liverpool. SEA-FISHERIES LABORATORY. 293 “ Histoire naturelle des Crustacés,” Muilne-Edwards named it Platycarcinus pagurus. This latter name appears to have been retained in many continental works up to quite recent years. . I have followed the classification of Borradaile,* and I give below a table compiled from the results of his work. CRUSTACEA DECAPODA | : | Natantia Reptantia (sub-orders) | | Palinura Astacura Anomura Brachyura (tribes) | Oxystomata Dromiacea Brachygnatha (sub-tribes) | | One be Oxyrhyncha . ee hayes (super-families) i Corystidae Portunidae, etc. Cancridae (families) al Pirimelinae Cancrinae (sub-familes) Cancer’ (genus) The main characters of the various divisions of the Decapod Crustacea are given below.t Natantia.—Rostrum well developed and compressed. Body compressed. First abdominal somite equal to rest. Stylocerite present. Second antennal scale large. In the legs basis and ischium never fused, and one fixed point in the carpo- propodal articulation. Male genital opening arthrodial. Abdominal limbs 1-5 well developed and used for swimming. * Borradaile, L. A. ‘‘On the Classification of the Decapod Crustaceans.’’ Ann. and Mag. Nat. Hist. (7), Vol. XIX, June, 1907. + These characters are abstracted from Borradaile’s paper. 294 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Rerrantia.—Rostrum reduced or absent, depressed if present. Body depressed. First abdominal somite smaller than rest. Stylocerite absent. Second antennal scale reduced or absent. In the legs generally a basi-ischium, and two fixed points in the carpo-propodal articulation. Male genital opening coxal and sternal. Abdominal limbs 1-5 reduced or absent, and not used for swimming. The four tribes belonging to the Reptantia are divided into two groups. I. Third legs like the first. Abdomen macrurous. Gnathobases of second maxillae narrow. Exopodites of maxillipedes with lash directed forward. Gulls numerous. (1) Parinura.—Carapace fused to epistoma. Rostrum small or absent. Inner lobes of second maxillae and first maxillipedes reduced. Body depressed. (2) Astacura.—Carapace free from the epistoma. Rostrum large. Inner lobes of second maxillae and first maxillipedes not reduced. Body sub- cylindrical. II. Third legs unlike the first, never chelate. Abdo- men rarely macrurous. Gnathobases of second maxillae broad. iixopodites of maxillipedes with lash directed inward. Grills few. (3) ANomuRA.—Carapace not fused with epistoma. Last thoracic sternum free, its legs differmg from the others. Abdomen anomurous. Movable antennal scale. Third maxillipedes narrow. (4) Bracuyura.—Carapace fused with epistoma. Last thoracic sternum fused with rest, its legs like the others. Abdomen brachyurous. No movable antennal scale. Third maxillipedes broad. SEA-FISHERIES LABORATORY. 295 The following are the sub-tribes of the Brachyura : — Oxystomara.—Mouth-field prolonged forward as a gutter. No female first abdominal limbs. Gills few. Female openings sternal. Dromracea.—Mouth-field square. First abdominal limbs present in female. Gills many. Female openings coxal. BracuyenatHa.—Mouth-field square. Female openings sternal. No first abdominal limbs in female. Gills few. The Brachygnatha are divided into two super- families. OxyruyncuHa.—Front part of body narrow. Distinct rostrum. Body more or less triangular. Orbits incomplete. BracHyruyncua.—Front part of body broad. Rostrum reduced or wanting. Body oval. Orbits com- plete. The Brachyrhyncha are sub-divided into fourteen families. I give here the chief characters of the one family—the Cancridae. CancripaAE.—Marine crabs with the branchial region not greatly swollen. Carapace broadly oval or hexagonal. Rostrum often wanting. Orbits com- plete. Male openings coxal. Second antennal flagella short. First antennae folded length- wise. Inner lobe on the endopodite in the first maxillipedes wanting. Legs generally not adapted for swimming. The two sub-families of the Cancridae are as follows :— PIRIMELINAE.—Carapace hexagonal. Epistoma sunken. CancrinaE.—Carapace broadly oval. Epistoma not sunken. 296 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. EXTERNAL CHARACTERS (Pl. I, figs. 1, 2, 8). The whole of the exterior of the animal is covered by a thick continuous chitinous exoskeleton or shell, which is highly calcified except between the movable somites of the abdomea and between the movable podo- meres in the appendages. The body may be conveniently divided into an anterior region—the Cephalon, a middle region—the Thorax, and a posterior region—the Abdomen. As in all the Decapoda the Cephalon and Thorax are fused to form the Cephalothorax. The Cephalothorax is by far the largest portion of the body, and is the only part seen from the dorsal surface. The Abdomen is much reduced and is a flap- hike structure closely applied to the ventral region of the cephalothorax between the bases of the walking legs. There 1s every reason to believe that the crabs and their relatives have arisen from primitive Crustaceans having a body divided up into a number of movable segments or somites. Hxtreme specialisation has taken place, especially in the cephalothoracic region, and it is in the Abdomen that one sees the nearest approach to this primitive external segmentation. A careful exami- nation, however, reveals the fact that there are five somites in the cephalic region, e¢ght in the thorax and sex in the abdomen—aneteen in all. Before entering on a description of the more complex parts it will be useful to examine the structure of a typical abdominal somite. The third abdominal somite of the female may be taken as a type (see text fig. 1). - This somite is flattened dorso-ventrally. On the SEA-FISHERIES LABG! 297 fa dian portion—the tergum (text fig. 1, t.\—whigh i ontinued into two he median ventral m each of the outer 3% @ppendage. Between the point of attachment of “eae appendage and the pleuron the ventral wall is known as the epimeron. Fic. 1.—Diagrammatic section through female abdomen. t.=tergum. m.a.= muscles of abdominal p.=pleuron. appendage. s.=sternum. h.g.=hind gut. é. =epimeron. pr.=protopodite. e.m. =extensor muscles of abdomen. ex.=exopodite. f.m.=flexor musclesof abdomen. en.=endopodite. The segment is connected with the two neighbouring segments by a thin uncalcified part of the exoskeleton— the arthrodial membrane. This allows of free movement between the segments. Hach segment articulates with the one in front by means of a pair of hinges placed at the outer and anterior part of the pleuron at each side. The appendages will be described in detail later. CEPHALOTHORAX. FE: Carapace. The terga and pleura of the cephalothorax are fused to form the large Carapace. ‘This is a broad shield the width of which is about 1} times as great as the length. 298 TRANSA IVERPOOTL BIOLOGICAL SOCIETY. Instead of t passes outw even sweep downwards the carapé ost horizontally and then sudder yasses down to the bases of the walk legs. An examination’ of a rough section of the aniz will show that at the base of the legs the carapace tv suddenly upwards and i 1s continuous with the membran wall of the spacious Branchial Chamber (PI. y, fig. Greeks). “The space between the ventral part of carapace and the base of the legs is so very small, moreover is so well guarded by long setae that no w ean enter the branchial chamber at this border, as is ease in the Macrura. There are, however, two open into the branchial chamber—the small posterior inh branchial aperture, above the coxopodite of the bends inwar pereiopod, and the larger anterior inhalent brag aperture, situated immediately in front of the coxo of the chela. The ventral part of the carapace | forward in front of the latter opening, and passing atom the mouth it fuses with the pre-oral cephalic sterna. T portion of the carapace which passes around the mouth turned inwards at each side to form a chamber which | immediately in front of the Branchial Chamber. T may be called the Pre-branchial Chamber. Its roof membranous and is fused on its inner side with epistoma and with the endopleurites of the two post- cephalic somites, and probably represents the epimera the third, fourth and fifth cephalic somites. The branchial Chamber will be described in detail section on Respiration. Both the dorsal and the inflected portions lateral region of the carapace were designatet ‘“branchiostegite’’ by Milne-Edwards because enclose the branchial cavity. Anteriorly the dorsal surface of the carapac SEA-FISHERIES LABORATORY. 299 bounded by a median portion between the orbits and two lateral portions. Similarly the posterior boundary consists of a median portion and two lateral portions. So that we may speak of these borders as the anterior, antero- lateral, posterior and postero-lateral respectively. The Anterior Border is situated between the orbits. The rostrum, which occupies the median portion of this region, consists of a median and two lateral lobes. It is continued ventrally as a median plate which separates the two cavities in which are lodged the eye peduncles. Hach of the lateral lobes of the rostrum passes downwards as the supraciliary lobe, which fuses with the anterior and inner region of the second antenna (PI. III, fig. 20, S./.). Passing outwards from the rostrum the anterior border of the carapace divides at each side into the supra-orbital and infra-orbital portions which form the boundary of the orbit. On its inner side the supra-orbital edge has the prominent swpra-orbital lobe which is close to the lateral lobe of the rostrum. ‘The inner boundary of the orbit is fused with the outer portion of the second antenna. The Antero-lateral Borders form an arc of a circle the centre of which is at the junction of the two outer grooves bounding the epibranchial region of the carapace (see below). Hach antero-lateral border is divided up into nine lobes by well-defined ridges. There is no definite distinction between the antero-lateral border and the postero-lateral border, but the latter may be said to commence at the posterior end of the ninth lobe. There _ is also a feebly marked lobe on the outer portion of the postero-lateral ridge. The Postero-lateral Border passes backwards and inwards. This border is well rounded and not so clearly defined as the anterior and antero-lateral borders. Immediately in front of this border there is the 300 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. postero-lateral ridge, which is continuous on its outer side with the antero-lateral border. At its outer edge it is coincident with the postero-lateral border, but as it passes . inwards it becomes quite distinct from the latter and dies away near the median line in front of the posterior border. The Posterior Border of the carapace is” horizontal, and is continuous behind with the tergum of the first abdominal segment. Areas of the Carapace. (Text fig. 2.) The dorsal surface of the carapace is divided up by means of small depressions into areas. The Cervical groove (C.gr.) separates the cephalic region of the carapace from the thoracic region. This groove 1s seen as a transverse median depression a little more than half way down the carapace. The width of this median groove is almost equal to the distance between the two supra-orbital lobes. | At each of its outer edges the median groove is continuous with a well-marked depression which commences at the posterior end of the fifth lobe of the antero-lateral border. This depression is curved, the convexity being in front. The median groove and its two lateral extensions together form the cervical groove. The Cephalic portion of the carapace is divided into the Facial and Gastric regions. | The Facial region is separated from the rest of the . cephalon by a faint transverse depression near the front of the carapace. The outer ends of the depression bend forward and terminate on the second lobe of the antero- lateral border. This region is divided into a median — Frontal region (/’r.) and two lateral Orbital regions (O7b.). The Gastric region is bounded behind by the — . A A A IL, LIE IE SEA-FISHERIES LABORATORY. 301 Cervical groove, and is composed of a median triangular portion having the apex pointing backwards and two lateral portions which end at the antero-lateral border. The median portion is divided into two anterior Proto- gastric regions (Pg.), a median anterior Mesogastric region (J/g.), a pair of posterior Metagastric regions (Mitg.), and a median posterior Urogastric region %. ge san 7 7 ge : ue Fic. 2.—Aveas of the Carapace. Fr.=Frontal region. Mb.=Mesobranchial region. Orb. = Orbital of Mib.=Metabranchial _,, - Hep. = Hepatic Bes Hb. =Epibranchial a Pg.=Protogastric ,, Card. = Cardiac ss Mg.=Mesogastric ,, : C.gr.=Cervical groove. Mig.=Metagastric ,, » B.gr.= Branchio cardiac groove. *Ug.=Urogastric _,, (Ug.). The lateral portions are known as the Hepatic regions (Hep.). Hach extends outwards to the antero- lateral border and is bounded behind by the outer part of the cervical groove. The Thoracic portion comprises that part of the carapace which lies behind the cervical groove. It is 302 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. divided by two longitudinal grooves—the Branchio- cardiac grooves (B.gr.)—into a median Cardiac region - (Card.) and two lateral branchial regions. Hach branchial region is made up of an anterior Mesobranchial region (J76.) and a posterior Metabranchial region (J/tb.) and a small inner Epibranchial region (/0.). The ventral inflected portion of the carapace is divided into two parts by a well defined groove, which may be termed the pleural groove, as it probably marks the separation between the cephalo-thoracic terga and pleura. It is along this groove that the carapace splits during ecdysis (see section on lNedysis). The pleural groove commences at the epistoma and passes outwards and slightly backwards until it almost reaches the posterior end of the seventh lobe of the antero-lateral border. Here it turns backward and runs parallel to the postero-lateral ridge, finally reaching the posterior border with which it becomes continuous. Thus the pleural groove divides the inflected portion of the carapace into an outer, or Sub-hepatic region, and an inner, or Sub- branchial region. The sub-hepatic region may be considered as an inflected portion of the tergum, and the sub-branchial as belonging to the pleural region. Milne- Edwards regarded the sub-branchial region as part of the . cephalo-thoracic epimera, but the inner walls of the branchial chambers undoubtedly represent the epimera. 9. Pre-oral Cephalo-thoracic Sterna. (Pl. III, figs. 19, 20.) Ventrally the median lobe of the rostrum passes backwards as a triangular plate, the apex of which points posteriorly. This plate, which is separated at its posterior end from the first sternum [antennulary sternum] (S*) TAS e Sr ™ aad a aa i ee tage OT mee tg er WR eet nme FT carte SEA-FISHERIES LABORATORY. 303 by a well-defined suture, forms a septum* between the articular cavities of the two optic peduncles. From the dorsal side of the sternal region the septum between the above-mentioned articular cavities is short and broad. On a level with the posterior end of these cavities there is a well-marked suture separating the septum from the first sternum. Immediately in front of the dorsal side of the ophthalmic articular cavities (0.m.c.) are two _ short calcareous plates near the median line, which stretch across to the roof of the carapace. These are the Procephalic processes (p.c.p.) to which are attached the anterior gastric muscles. _ The First Sternum (S1) lies in the segment of the first antennae (ant/e.) and separates the articular cavities of these appendages. Owing to the depth of the sternum in this region its relationship to the articular cavities is best seen from the dorsal side of the sternum. It consists of a median piece lying between the articular cavities of the antennules, and of two lateral expansions which form the posterior boundaries of the articular cavities. Viewed laterally the sternum is seen to have a comparatively gr at depth. About half way down the anterior face of th ~ sternum is a concavity into which fits a process from ‘he septum between the ophthalmic articular cavities. From the ventral side the ‘rst sternum bounds the posterior and inner sides of the + ckets of the antennules, and the lateral prolongations extend as far as the bases of the second antennae. *In the present Memoir the optic peduncles are not regarded — as modified appendages, and I shall not regard the region of the body from which the eyes arise as the first segment, nor shall I speak of the septum between the articular cavities of the optic peduncles as the first sternum. a Ey Ct. * er 304 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Huxley* in his short account of the crab states that the ophthalmic and antennulary sterna are fused, and that the suture is between the fused sterna and the rostrum. I am of the opinion that the whole of the sternum behind the suture belongs to the antennulary somite alone, and that the septum separating the articular cavities of the optic peduncles is a posterior prolongation of the rostrum, as described above. An examination of the sternum from the dorsal side (Pl. IIT, fig. 19) shows that the suture is on a level with the posterior boundary of the ophthalmic articular cavity ; so that, if Huxley’s view be accepted, we have the ophthalmic sternum entirely behind the articular cavity of its own somite! It is much more reasonable to conclude that the suture separates the ophthalmic septum from the antennulary sternum. The Epistoma is a broad plate in front of the mouth , and immediately behind the first sternum. It represents the united sterna of the second (antennary) (S?) and third (mandibular) (S*) somites. Its anterior border is concave in front. The two lateral borders gradually slope inwards towards their posterior ends. The posterior border is deeply concave behind and bounds the front edge of the mouth. The middle part of the anterior border touches the posterior edge of the first sternum and the two outer portions bound the posterior edge of the second antenna. The lateral borders are in contact with the membranous roof of the pre-branchial chamber. From the middle of the anterior border of the ventral side of the epistoma a median groove passes backwards but does not extend as far as the posterior border. From _ *T. H. Huxley, Manual of the Anatomy of Invertebrated Animals, 1877, pp. 340-345. - — ay Eo i, - SEA-FISHERIES LABORATORY. 305 - the posterior edge of this groove a slight depression passes - itwards at each side parallel to the anterior border. _ This depression probably marks the boundary between the -antennary and mandibular sterna. This groove is better defined on the dorsal side of the epistoma. be 03 The Labrum (Pl. ITI, fig. 20, dab.) is a soft fleshy Jobe attached to the middle region of the Se border of the epistoma. It is surrounded near the middle by a ealeareous ring which gives off a median posterior q prolongation. At each side of this median plate is a soft fold. eae 8 Post-oral Cephalo-thoracic Sterna | (Pl. I, figs. 2, 3, Text fig. 3). i 1 a if These are all fused together as a single oval-shaped ate situated between the bases of the paired post-oral =a appendages. Transverse grooves are present which mark the division of this region into | ae segments or somites, and which mark the places at which ; "the sterna grow inwards to form the endosternites of the _ endophragmal system. “a The surface of the fused sterna is concave laterally ; 2 order to accommodate the abdomen, which is always in 1 flexed condition. This concavity is especially well marked i in the males. The surface of the sterna is, how- a... convex antero- posteriorly. Bs ‘i On the sternum of fifth thoracic somite are two small tubercles (P.) which fit into two concavities on the abdomen and thus form an effective locking apparatus which keeps the abdomen in position. These are. _ especially large in the males. 3 oe The sternum of the sixth thoracic somite of the female bears a pair of large openings which are Be ‘ternal i openings. b 306 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The sterna of the last four thoracic somites characterised by a median groove which marks the at which the “ Median plate” of the endophragmal syst has grown inwards. ‘The anterior end of this medi groove is marked by a very deep depression which t situated at the posterior end of the fourth thoracie sternum. ) At the outer and posterior corners of each sternum are backwardly directed areas—the “ epistert a Fic. 3.—Ventral view of post-¢ cephalothoracic sterna (male). d F.S. = Fused sterna of the two. nf t] post- oral cephalic and the three thoracic somites. 4.ts. —8.ts. = Sterna of the 4th to 8th thoracic somites. fip.s. = Episterril P. = Sternal papilla of abdominal locking apparatus. p a (f'ps.) which run for a short distance alongside the following sternum, from which they are separated by distinct sutures. Between each episternum and _ t corresponding sternum is a slight groove which is not 1 distinct in the edible crab. In Portunus and other ere however, this groove is much more distinct so as suggest a complete separation between the sternum episternum. This probably explains why Brooks* s * Brooks, Handbook of Invertebrate Zoology. SEA-FISHERIES LABORATORY. 307 that the episternum 1s antervor to the outer end of its own sternum. He has evidently mistaken the groove mentioned above for a true suture, and has therefore concluded that the episternum belongs to the following sternum. The last thoracic sternum has no episterna. At the anterior end of each episternum is a small concavity into which fits the ventral hinge of the coxopodite of the appendage of that somite. The sterna of the last two cephalic and the first four thoracic somites (/.S.) are fused together, without any sign of separation into distinct segments as in the posterior region of the thorax.t There is, however, a slight evidence of a division in front of the fourth sternum of the thorax. That portion of the thoracic sterna which is covered by the abdomen is characterised by the absence of setae. There are long setae along the outer edges of the episterna, and also on that portion of the fused sterna belonging to the two last cephalic segments and the. first four thorac’~ segments. i f the fourth thoracic sternum the outer edges ©: _rna are turned up vertically. Tt post-oral cephalic sternum has two lateral proces: - ich project forwards and give support to the Metasic*:- The metastoma is a fleshy lobe forming the posterior '+ of the mouth. A Ceplalic epimera. In the first two cephalic somites it is difficult to identify the epimera, but the latter are probably repre- sented by the region between the outer portion of the articular cavities of these somites and the carapace. + The two post-oral cephalic sterna, which are represented by two narrow bars at the extreme anterior end of the fused post-oral sterna, are separated from each other, however, by transverse sutures. W a 308 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The epimera of the third (mandibular) and the two last cephalic somites (maxillary) are probably represented by the membranous roof of the pre-branchial chamber at each side (Pl. III, fig. 18, 7.br.). This is continuous behind with the thoracic epimera. 5. Thoracic epimera (Plate IIT, fig. 18, epm. 6-12). The thoracic epimera are represented by a continuous plate at each side forming the inner wall of the branchial chamber. This is the “flanc”’ of Milne-Edwards. The lower border of the epimera commences immediately above the base of the thoracic appendages. ‘They pass upwards and inwards and are continuous above with the membranous roof of the branchial chamber. At the pecterior end they extend upwards almost to the carapace, from which they are only separated by short muscles which pass from the summit of the epimera to the pace. At the anterior end the epimera are much shallower and become continuous with the roof of the branchial chamber some distance below the carapace. The fused thoracic epimera form an extremely convex wall which is divided up into segments by vertical sutures, which correspond to the lines of separation between the various somites of the thorax. In this way the epimera are divided up into seven portions. The epimera of the first and second thoracic somites are completely fused, and there is no groove separating them, but apart from this there is one segment of the fused epimera for each of the remaining thoracic somites. The epimeron of the fourth somite is particularly broad. That of the last thoracic somite is not bounded posteriorly by SEA-FISHERIES LABORATORY. 309 a groove, but is continuous with the sternum of the same segment. In their natural position the gills he upon the thoracic epimera. THe ABDOMEN. The abdomen is continuous with the posterior part of the cephalothorax. The connection is effected by means of an arthrodial membrane, which allows of considerable movement between the two regions. The abdomen is small and in its natural position is closely apphed to the sternal region of the thorax. This region differs in the two sexes, being much broader in the female than in the male. This character provides a useful and ready method of distinguishing between the two sexes. There are other differences which require a more detailed examination. Female. GEriene 2, BIN fie. 32, Pl V, feo 34.) This consists of six somites and the telson, all of which are freely movable. When lying in position it extends as far forward as the posterior end of the sternum of the third thoracic somite. The locking arrangement for keeping the abdomen closely applied to the thoracic sternum is not so well developed as in the male. It consists of two extremely small tubercles on the fifth thoracic sternum which fit into two slight depressions at the postero-lateral corners of the ventral side of ixth abdominal somite. The total length of the ab 21 times as much as its greatest width. There are four pairs of appendages, one pair _ borne on the second and on each of the three following” somites, respectively. 310 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. On the dorsal side of the abdomen the terga are separated from the pleura by two longitudinal grooves. Ventrally the median portion is covered by a thin uncaleified cuticle and the outline of the hind-gut is CLeaPLY Seek. 7 The hind-gut opens on the ventral side of the telson at the anus. Only the first somite requires any special comment. The upper side of this somite is prolonged forward as a thin triangular flap, the apex of which points anteriorly. This triangular portion is covered by the carapace, only a narrow region at the posterior end of the somite being exposed. All around the anterior edge of this somite is a thin membrane which is continuous with the posterior region of the cephalothorax. The first two somites are hollowed out laterally to provide free movement for the last pair of thoracic legs. Mia lie” (Pie tiesia)): When lying in position the abdomen extends slightly in front of the middle of the fourth thoracic sternum. It is shghtly shorter than the female abdomen and much narrower. As in the latter, the sides of the first two somites (and also part of the third) are hollowed out and pass round the inner sides of the last pair of thoracic appendages. The first somite has the same arrangement as in the female. The anterior part of the dorsal side is triangular and is covered by the carapace. ene e third, fourth and fifth somites are fused together ere is absolutely no movement between them. s marking their separation still persist. are only two pairs of appendages which are present on the first and second somites respectively. SEA-FISHERIES LABORATORY. esd al These appendages are peculiarly modified to act as copulatory organs (see sections on Appendages and Repro- ductive System). The male abdomen is much more closely applied to the thorax than is the case in the female. ‘This is partly due to the small number of appendages and also to the very effective locking apparatus. The latter is similar to that described in the female and the position of the parts is the same, but the tubercles on the thoracic sternum are much larger, as is also the case with the concavities on the sixth abdominal somite. Below are given the measurements of the abdomen of a male and female, both having a carapace breadth of 23°9 cm. FEMALE. MALE. No. of | Somite.| Greatest | Greatest Greatest | Greatest length. width. length. width. mm. mm. mm. mm. di LZ 25 | 174 2? 2 Bien, Wamce 17 3 | 7 | 30 | ve 23 4 8 oe, 8 20 5 10 35 9 17 6 20 35 | 13 16 Telson fa Ls 21 13 13 Total iene 88 mm. Total length, 75 mm. External apertures. The external openings are as follows: — The Mouth—a median aperture on the ventral side of the cephalic region between the mandibles. $12 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The Anus—a median aperture on the ventral side of the telson. . The Excretory Openings—one pair. ‘These are situated at the base of the second antennae on the ventral side. ach is covered by an operculum. The Female Reproductive Openings—one pair. These are two large apertures on the sternum of the sixth thoracic somite. The Male Reproductive Openings—one pair. These are situated on the ventral side of the coxopodites of the last pair of thoracic appendages. APPENDAGES (Plate II). There are five pairs of appendages on the head and eight pairs on the thorax. There are four pairs of abdominal appendages in the female and only two pairs in the male. The appendages are as follows: — Cephalon. Somite I.—1st Antennae (Antennules). 7 I.—2nd Antennae. he I1J.—Mandibles. y IV.—1st Maxillae. us V.—2nd Mavxillae. Tony ay Somite VI.—1st Maxillipedes. i VIl.——2nd Maxillipedes. + VIII.— 8rd Maxillipedes. _ IX.—1st Pereiopods. ¢, X.—2nd Pereiopods. XI.—8rd Pereiopods. i XII.—4th Pereiopods. - XIII.—5th Pereiopods. Female. Male. Abdomen. Somite XIV.—Absent. 1st Pleopods. . XV.—Ist Pleopods. | 2nd Pleopods. A XVI.—2nd Pleopods.| Absent. »5, XVII.—3drd Pleopods. | Absent. » X&VIII—-4th Pleopods.| Absent. Ye XIX.—Absent. Absent. SEA-FISHERIES LABORATORY. ole The First Antenna or Antennule (PI. II, fig. 4, Pl. III, fig. 20) is situated in a deep depression on the ventral side of the cephalic sternum (s.a.1). This depression or socket is bounded in front by the rostrum (rost.), and behind by the lateral expansion of the first sternum (s'). The outer boundary is formed by the inner edge of the second antenna (ant.), and the inner boundary by the median portion of the first sternum. The appendage consists of a broad basal joint, from which is given off on its inner side a two-jointed portion. ‘These three pieces together form the protopodite (prot.). From the end of the distal segment of the protopodite arise two many- jointed flagella—an inner endopodite (end.) and an outer exopodite (ex.). The exopodite is the larger of the two, and bears on its inner side a tuft of long setae. The ‘“ olfactory ’ setae are small setae on the ventral side of the exopodite (see section on Sense Organs). On the dorsal side of the basal segment of the protopodite is a longitudinal groove covered with long setae. ‘This groove marks the place where the auditory sac opens to the exterior in the young animal. In the adult crab this groove is completely closed, although it remains open a short time after ecdysis. In their natural position the three parts of the protopodite are folded on one another. The second segment is closely applied to the inner side of the basal _ segment. ‘he third segment is bent back along™~the dorsal side of the second, and its distal end hes in an excavation made for its reception in the dorsal wall of the basal segment. Second Antenna (PI. II, fig. 5, Pl. ITI, fig. 20). This consists of a large basal portion (prot.) which is fused to the carapace, and a distal flagellum, which consists of two long basal segments and a number of short rings, 314 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. arising from the anterior and inner region of the basal portion. At the posterior and outer corner of the large basal segment is the operculum (op.), which covers the external excretory opening. ‘This operculum probably represents the covopodite and the larger basal portion the basipodite, the two together forming the protopodite. The flagellum probably represents the endopodite. The outer edge of the basipodite is fused to the sub- hepatic region of the carapace. Backward processes from the supracilary (S./.) and supra-orbital lobes fuse with the anterior end of the basipodite. The inner and posterior corner of this segment is in contact with the lateral. portion of the first sternum, and the posterior border of the same segment is in contact with the epistoma. The Mandible (Pl. II, fig. 6) hes at the side of the mouth. The main portion is an elongated strongly calcified structure which is divided into two parts—an inner part, which projects over the ventral region of the mouth, and acts as the “jaw,” and an outer part, the apophysis (apoph.), to which are attached the tendons of the mandibular muscles. At the outer extremity is the tendon of the external adductor (¢.ev.ad.). Behind this, attached to a small projection, is the tendon of the external abductor (¢.ev.ab.). To the posterior and inner side of the apophysis is attached the tendon of the internal adductor (¢.cnt.ad.). The internal abductor arises from the apophysis on the inner side of the base of the tendon of the external adductor. There is no tendon for the internal abductor. Anteriorly the mandibular palp (md. palp.) arises from the inner side of the apophysis. The mandible is hinged to the epistoma by means of a small projection below the palp. There is no definite hinge posteriorly, but the posterior border of the inner region SEA-FISHERIES LABORATORY. 315 of the apophysis is attached to the metastoma by means of a somewhat flexible membrane. The First Maxilla (PI. I, fig. 7, Pl. IV, fig. 26), which arises immediately behind the mandible, is small and is made up of a protopodite and endopodite. The exopodite is absent. The protopodite is on the inner side and is composed of two distinct pieces—a narrow proximal coxopodite (C.) and a larger basipodite (B.) which is external to the coxopodite. The endopodite (end.) arises from the outer side of the basipodite, and consists of a broad proximal leaf-like region and a narrower distal region. From the distal extremity of both parts of the protopodite arise fairly strong setae. The Second Maxilla (Pl. II, fig. 8, Pl. IV, fig. 27) consists of an inner protopodite, a median endopodite (end.) and an outer evopodite (Scaph.). The protopodite is composed of a coxopodite (C.) and a basipodite (B.), each of which is bilobed. The two lobes of the coxopodite are long and slender, and are clearly separated from one another. Those of the basipodite are broader, and the separation between the two lobes is only partial. On the outer side of the basipodite is the small endopodite, which ends in a long narrow process. On the outer side of the endopodite and arising from the basipodite, is the large modified exopodite which is known as the scaphognathite (Scaph.). This is a broad plate of irregular shape which lies in the pre-branchial chamber. By means of its rapid and complicated movement it bales the water out of the branchial chamber. | In the First Maxillipede (P1. II, fig. 9) the protopodite is on the inner side. The cowopodite (C.) is small and richly clothed with setae, and the basi podite (B.) is a long lamella having two rows ot setae on its outer edge. The endopodite (end.) is between the exopodite and the proto- 316 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. podite. It is membranous, the proximal half being flattened laterally and the distal half dorso-ventrally. The evopodite (ex.) is long and slender and consists of a long proximal segment, which is as long as the endo- podite, and a distal many-jointed flagellum (flag.) which in its natural position projects inwards at right angles to the proximal segment. During life this flagellum is exceedingly active. From the outer side of the protopodite arises the long flabellum (flab.) (or epipodite). This is a long narrow membranous plate which passes back into the branchial chamber above the gills. The proximal portion of the flabellum is broad and leaf- like. The Second Maxillipede (Pl. II, fig. 10) has the exopodite and flabellum in the same position as in the previous appendage. The flabellum (flab.), however, is much shorter than that of the first maxillipede, and lies along the upper portion of the thoracic epimera and below the gills. The protopodite is much reduced, but the proximal coxvopodite* (C.) and the distal baszpodite (B.) can still be made out. The endopodite is comparatively larger than the same part in the first maxillipede. It arises from the basipodite and is divided into five movable segments. The first or proximal segment—the ischiopodite (I.) is small. The second segment or meropodite (M.) is the longest, and equal in length to the other four segments. The three distal segments are small, and between the second and third segment the endopodite turns inwards, the distal segments being at right angles to the meropodite. The names of the third, fourth and fifth segments are carpopodite (C.1), propo- * The following abbreviations are sometimes used :—coxva coxopodite; basis = basipodite; ischiwm = ischiopodite ; meros mieropodite ; carpos = carpopodite; propos = propodite ; dactylos dactylopodite. oil tt SEA-FISHERIES LABORATORY. oes dite (P.) and dactylopodite (L).) respectively. Arising from the appendage immediately in front of the base of the flabellum is a podobranch (pod. br.) (see section on Respiratory Organs). The Third Maxillipede (PI. II, fig. 11, Pl. LV, fig. 30) is built on a similar plan to the previous appendage. ‘The basis and the ischium are fused together to form the basi-ischium (B.-I.). The podobranch (pod. br.) is very small and arises from the coxopodite. The flabellum (flab.) lies on the lower part of the thoracic epimera below the gills. The endopodite and exopodite (ex.) are closely applied together and are much flattened so as to form with the same appendage of the other side an effective operculum closing over the remaining mouth parts, and preventing the exhalent current of water from the branchial chamber from passing out except in front of the scaphognathite. The mandibles, maxillae and maxillipedes all lie around the mouth in the large depression between the anterior parts of the sub-branchial regions of the carapace. The ventral side of the third maxillipedes is on a level with the sub-branchial region. As _ the flabellum of this appendage passes back into the branchial cavity, it passes along the front of the anterior inhalent branchial aperture, and reduces the size of the aperture considerably. At this point the flabellum* is also richly clothed with strong setae, which probably act as a d “ straimer ” in conjunction with the setae present on the front part of the coxa of the chela (see section on Respiratory Organs). The First Pereiopod (or chela) (Pl. II, fig. 12, Pl. ITI, * The coxopodite of the third maxillipede is prolonged outwards, and bounds the inner part of the inhalent aperture. The flabellum bounds the outer part. Both are richly clothed with setae on their posterior faces. 318 TRANSACTIONS LLVEREFOOL BIOLOGICAL SOCIETY, fig. 21) is the largest appendage in the body. It consists of seven segments (or podomeres). A comparison with the third maxillipede indicates that the two proximal segments belong to the protopodite, and the remaining five to the endopodite. There is no exopodite present. The seven segments have the same names as the similar parts in the third maxillipede. With the exception of the second and third segments, which are fused together to form the basi-ischium (B-I.), all the parts are freely movable. The basi-ischium has a thin groove running around it, which marks the separation of this fused portion into its two constituent parts. This groove is known as the fracture plane because it is at this point that the animal fractures the limb during the process of self- amputation (see section on Autotomy). The two distal segments of the limb are slightly modified to form the pincer which constitutes an effective prehensile organ. Hach of the movable segments swings in a different plane, so that the combined movement of the whole appendage is a very complete one. The coxopodite (C.) articulates with the body by means of two hinges, one being dorsal (Pl. III., fig. 21, d.) and the other ventral (v.). The dorsal hinge is attached to the antero-ventral corner of the epimeron of the fourth thoracic somite, and the ventral hinge articulates at the postero-lateral corner of the sternum of the same segment. Thus the motion of the coxopodite is in a horizontal plane, moving backward and forward. ‘The fused basi-ischium (Z.-J.) articulates with the coxa by an antero-dorsal (d!) and a _postero- ventral hinge (v1), and the movement is upwards and downwards in a plane making an angle of about 45° with the vertical. The meros (J/.) has very little movement. Its two hinges are antero-dorsal (d?) and postero-ventral respectively (v?), and the small degree of movement of SEA-FISHERIES LABORATORY. 319 which this segment is capable is almost in a vertical plane. The two hinges of the carpos (C.!) are situated dorsally (d?) and ventrally (v?), and the segment moves forward and downward. The propodite (P.) has two hinges—dorsal (d*) and ventral (v*). The former is external to the latter, and the segment moves forward and slightly upward. In the dactylos ().) the hinges are horizontal and the segment swings in a vertical plane. The dimensions of the various segments of the chela in a female crab (carapace breadth 23°5cm.) are as follows :— Anterior length. Posterior length. Coxopodite ... ve (penne ceo Ll seman Basi-ischiopodite ... 17 ,, - Opa Meropodite ... ae eee a iy alee Carpopodite... ee gee BAS Oi Propodtte ... DO: Se oye, FOO iets, Dactylopodite ee ewe Laan Oh are The dorsal sides of the basi-ischium and of the meros are flattened so that they can be closely applied to the anterior portion of the sub-branchial and_ sub-hepatic regions of the carapace, and in these places setae are absent from the carapace. Between the meros and the carpos the limb is capable of bending on itself, so that the anterior borders of the propodite and the carpos become closely applied to the anterior borders of the basi-ischium and the meros. On the dorsal side ef the basi-ischium and meros there are irregular grooves. These are the lines of absorption (Pl. II, fig. 12, abs.) (see section on Ecdysis). Pereiopods 2-5 (Pl. II, fig. 13). These are known as the “walking legs.” Their essential structure is the same as that of the chela. The one obvious difference 1s that in all the walking legs the propodite has not an i 390 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. outgrowth which, in conjunction with the dactylos, forms a pincer. In other words, the walking legs terminate in a single claw, and are not chelate. The three terminal segments are capable of being flexed upon the proximal segments. ‘This flexion is in a vertical plane. Pleopods (Female) (Pl. II, fig. 17). There are four pairs of appendages on the female abdomen, one pair being situated on each of the second, third, fourth and fifth somites respectively. They are all similar in structure. Hach pleopod is attached to the abdomen by a basal piece—the protopodite (prot.). From this arise two long pieces an outer exopodite (ex.) and an inner endopodite (end.). The exopodite is almost cylindrical in section, and about half as long as the abdomen. From the outer and inner edges of the exopodite rows of setae arise. Each seta has short fine branches given off from each side of the central stem. The endo- podite is about as long as the exopodite. About one-third of its length from the base is a well-defined transverse groove. The setae are arranged, as in the exopodite, along the outer and inner edges, but they arise in small bundles. The setae are very long and do not bear off- shoots except near the tip, where there are a few very fine short branches. The eggs are attached to the endopoditic setae. Pleopods (Male) (PI. II, figs. 14, 15, 16). There are two pairs of abdominal appendages in the male, which are situated on the first two somites. Both pairs are greatly modified and act as copulatory organs (see section on Reproductive Organs). First pair (Pl. II, fig. 14). Hach consists of twe a broad basal portion, probably the protopodate parts | (prot.), and an elongated distal portion, which is rolled | SEA-FISHERIES LABORATORY. 321 on itself longitudinally to form a tube. This distal portion probably represents the endopodite (end.). The two basal portions fuse in the middle line, thus forming a tunnel-like structure extending backward below the second somite. Below the fused basal portions of the first pleopods arise the second pair of appendages (Pl. II, fig. 15). Each consists of two parts—a horizontal rod (prot.) projecting posteriorly, and a vertical rod (end.) attached to the posterior end of the first portion. The vertical rod is divided into two parts by a transverse groove. The horizontal rod probably represents the protopodite, and the vertical portion is the endopodite. There is no trace of an exopodite on any of the male pleopods. The vertical rod-like portion of the second pleopod fits into the tube of the first pleopod. ENDOPHRAGMAL SKELETON (PAPAL EL fers 138) Wext ties: (4.79, °6, 7). The post-oral region of the cephalothorax has an extremely complex system of internal plates, known as the endophragmal skeleton. Essentially this system may be said to consist of a number of inwardly-projecting plates arranged transversely so as to divide up the interior of the cephalothorax into a series of irregular compartments. Each partition, or arthrophragm, arises at the junction of two somites, and is formed by an igeneiae of the sternal and epimeral ° exoskeleton between these somites. Thus, each plate of the endophragmal skeleton is double, and is composed of two flattened plates of exoskeleton which are closely apphed together. The primary function of the endophragmal system is 322 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. to afford attachment for the muscles of the proximal region of the appendages in this region of the body. It is also useful in supporting and protecting certain portions of the viscera. Although at first sight the arthrophragms of the first five post-oral cephalothoracic somites differ in a marked degree from those of the posterior thoracic region, it will be shown that all are built on the same plan. DeEscRIPTION oF A TypicAL ARTHROPHRAGM (Text fig. 4). The fourth thoracic arthrophragm (between the fourth and fifth thoracic somites) may be taken as a type. It is a vertical partition extending inwards at each side from the line of junction of the fourth and fifth thoracic epimera. ‘The portion of the partition in contact with the thoracic sternum arises between the fourth and fifth thoracic sterna. Thus we may distinguish between two kinds of plates, viz., those growing inwards from the epimera—the endopleurites (Pl. III, fig. 18, ep., also Text figs. 4,5, 7), and those arising from the inner side of the sternum—the endosternites. Hach arthrophragm consists, therefore, of an outer endopleurite and an, inner endosternite at each side of the middle line. The two endosternites in the arthrophragm under discussion are separated from each other in the middle line by the median plate (fig. 18, med. p.), which is an ingrowth from the median suture present on the last four thoracic sterna. The plates of which the arthrophragm is composed are sometimes known as the * apodemata.”’ ‘ The Endosternite is irregular in shape and has five principal borders. | The median border is vertical, and is the part ft ‘aa endosternite. in contact with the median plate. SEA-FISHERIES LABORATORY. Bye) The sternal border (Text fig. 4, S6. s.) 1s in contact with the sternum, and forms the ventral boundary of the endosternite. The articular border (Ab. s.) passes upwards and out- wards, and is equal in length to the sternal border. It is connected with the arthrodial membrane in contact with the coxopodites of the fourth and fifth thoracic appendages. ] Epimeton |) E ndopleurite, E ndosternite, E Median plate, ma Sternum. Fic. 4.—Diagram of a typical arthrophragm. Db.p. = dorsal border of the endopleurite. Db.s. = dorsal border of the endosteraite. Eb.p. = epimeral border of the endopleurite. Ab.p. = articular border of the endopleurite. Ab.s. = articular border of the endosternite. Sb.s. = sternal border of the endosternite. A.F. = apodemal foramen. The outer border passes inwards and upwards, and at its upper and lower ends fuses with the endopleurite. This fusion is interrupted in the middle region of the border by the large apodemal foramen (A.F’.) which lies between the endosternite and endopleurite. The inner part of the dorsal border (Db. s.) passes 324 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. upwards and outwards from the median line, describing almost a semi-circle. The upper edge of the semi- circle almost reaches the median lne. Thus the inner portion of the dorsal border of each side surrounds an almost closed cavity, which corresponds to the * sternal canal” of the Macrura. The Endopleurite is rectangular in shape, and its length is about twice as great as its width. Four borders may be distinguished. The inner border is in contact with the outer border of the endosternite at its upper and lower ends. In the intermediate region it forms the outer boundary of the apodemal foramen. The articular border (Ab. p.) 1s in contact with the upper part of the arthrodial membrane connecting the coxopodites of the fourth and fifth thoracic appendages. The epemeral border (ib. p.) is in contact with the fourth and fifth thoracic epimera. The dorsal border (Db. p.) bounds the dorsal free end of the endopleurite. Above the apodemal foramen the _ endopleurite becomes fused on its posterior face with the following arthrophragm, and the anterior face of the arthrophragm under discussion becomes fused with the preceding endopleurite. All the arthrophragms of the post-oral cephalo- thoracic region are built on the above plan, that is to say, each somite has one endosternite and one endopleurite at each side. But in some cases the homology is very much disguised. The last five thoracic arthrophragms are very similar to the one described, but the anterior arthrophragms are extremely reduced. It is, therefore, advisable to describe the endophragmal skeleton in two parts, SEA-FISHERIES LABORATORY. B25 (1) The last five thoracic arthrophragms, beginning in front and working backward (posterior thoracic). (2) The two post-oral cephalic arthrophragms and the first three thoracic arthrophragms, beginning behind and working forward (anterior post-oral). (1) Postertor T'Horacic ENDOPHRAGMAL SYSTEM (PESKIT, figs 1s;-and text, fig. 9). This consists of the arthrophragms of the last five thoracic somites. The median plate commences at the posterior end of the fourth thoracic sternum. At first it 1s extremely shallow, but as it proceeds posteriorly it increases in height. It is present in the last four thoracic somites. As in other parts of the endophragmal system, the median plate is composed of two closely applied portions of the exoskeleton. In the fifth thoracic somite these two parts remain separate, and the cavity between them opens to the exterior at the posterior end of the fourth thoracic sternum. Each endosternite is at right angles to that part of the sternum from which it arises, and similarly each endopleurite arises at right angles to the epimeron. If the sternum were horizontal throughout: its entire length, and also if the epimeral wall at each side were vertical, the endophragmal system would be represented by a series of vertical partitions arranged one behind the other. This is the case in the Macrura. In the Brachyura, however, neither the sterna nor epimera follow this arrangement. The thoracic sternum is extremely convex antero- posteriorly and has an extreme upward tilt at its posterior end. ‘The epimeral wall, instead of having a flat surface, is extremely convex on its outer face. The shape of the sternum and of the epimeral wall gives rise to much 326 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. complexity in the endophragmal system of the last five thoracic somites. The endosternite and the endepleurite of the same arthrophragm instead of being in the same plane, as in the Macrura, may be situated at a consider- able angle to each other, so that it is difficult to believe that they belong to the same segment. The fifth endos- ternite is almost vertical, but the succeeding endosternites incline more and more forward until the last arthro- phragm is practically horizontal. The endopleurites of each arthrophragm become fused with the anterior face of the following arthrophragm, and thus we have each somite divided into four chambers. There is an outer chamber at each side lying between two consecutive endopleurites, and bounded on the outer side by the epimeron and on the inner side by the backward growth of the endopleurite. These chambers may be called the Plewral muscle chambers (Text fig. 6, P.). There is also an inner chamber at each side, lying between two consecutive endosternites, and separated from one another by the median plate. We designate these the Sternal muscle chambers (Text fig. 6, S.). These pleural and sternal muscle chambers contain the muscles which work the two basal segments of the appendages in this region. | The muscle chamber of the last walking leg is not divided into parts owing to the absence of a separate endopleurite in this somite. Therefore this last muscle chamber may be known as the Plewro-Sternal muscle chamber (Text fig 6, PS.). Each of these chambers has an antero-lateral prolongation, which extends forward as far as the posterior face of the fourth thoracic arthro- phragm. The fourth thoracic arthrophragm (Text fig. 5, A.) arises between the fourth and fifth thoracic somites. This arthrophragm has already been described, SEA-FISHERIES LABORATORY. By AG The fifth thoracic arthrophragm (Text fig. 5, B.) arises between the fifth and sixth thoracic somites. All the parts are very similar to those described in the fourth arthrophragm. The sternal border is shghtly more Fic, 5.—Anterior view of the left side of thoracic arthrophragms. A.=4th thoracic arthrophragm. B. =5th thoracic arthrophragm. C. = 6th thoracic arthrophragm. D.=7th thoracic arthrophragm. (The parts are shaded as in Fig. 4). g.=line of fusion with the following arthrophragm. h.=line of fusion with the 3rd thoracic endopleurite. k. =line of fusion with the 4th thoracic endopleurite. l. = line of fusion with posterior face of the preceding thoracic endosternite. m.=antero-lateral extension of pleuro-sternal muscle chamber. n.=line of fusion with the 5th thoracic endopleurite. o.=line of fusion with the 6th thoracic endopleurite. p.=line of fusion with the 6th thoracic endosteraite. arched. ‘The apodemal foramen is not quite so large. There is an additional cavity left in the dorsal side of the endosternite at each side (m.) ‘This is formed by the , i 398 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. anterior prolongation of the last pleuro-sternal muscle chamber. The endosternite is almost vertical, but there is a slight forward tilt. The endopleurite is slightly concave on its anterior face, and its plane is slightly posterior to that of the endosternite. The border of the endosternite surrounding the sternal canal has a slight notch. Around the foramen of the pleuro-sternal muscle chamber the endosternite of this arthrophragm fuses in front with the fourth endosternite (/.) and posteriorly with the sixth endosternite. Similarly along the outer border of the endosternite, above the apodemal foramen, this arthro- agi is fused in front with the fourth endopleurite (4) id with the sixth endopleurite. sixth thoracic arthrophragm (‘l'ext fig. 5, CU.) veen the sixth and seventh thoracic somites. ‘The endosternite is convex on its anterior face, and its plane is inclined considerably forward. Its median border is longer than in the previous arthrophragms. The notch in the sternal canal is much more pronounced than in the fifth arthrophragm. The upper border of the sternal canal is bent posteriorly, and its inner tip becomes fused with the upper edge of the median plate in the last somite. The dorsal border is fused with the anterior (or dorsal) edge of the last arthrophragm. In this way the seventh endosternite is completely roofed over and cannot be seen clearly until the sixth endosternite is removed. As in the previous arthrophragm, there is a large foramen in the dorsal region of the endosternite through which the pleuro-sternal muscle chamber passes (m.). The endopleurite is very similar to that of the fourth arthrophragm. At the junction of the endosternite and endopleurite this arthrophragm fuses in front with the fifth endopleurite (n.), and behind with the seventh endo- SEA-FISHUERIES LABORATORY. 329 pleurite. Also at the edge of the foramen bounding the pleuro-sternal muscle chamber this endosternite 1s fused in front to the fifth and behind to the seventh endosternite (/.). The seventh thoracic arthrophragm (Text fig. 5, D.) lies between the seventh and eighth thoracic somites. The endosternite is inclined at an angle of 50° to the vertical, the upper border being anterior. It is almost completely covered by the overhanging sixth endosternite. The median border is very deep and the sternal canal is very small. The dorsal border is almost level, and partly bounds the ventral side of the pleuro-sternal muscle chamber. The endosternite does not completely surround this chamber as in the two previous arthrophragms.. The sternal border is inclined at a considerable angle to the horizontal. ‘The apodemal foramen is small. The plane of the endopleurite is almost at right angles to that of the endosternite. At the junction of the endosternite and’endopleurite this arthrophragm fuses in front with the sixth endopleurite (0.), and where the endosternite borders the pleuro-sternal muscle chamber there is a fusion with the sixth endosternite (p.). The eighth thoracic arthrophragm (PI. III, fig. 18, e. st. 15) lies at the posterior end of the last thoracic somite. In this somite there is no separate epimeron. It is probably fused with the sternum. The arthro- phragm, therefore, shows no division into endosternite and endopleurite. It may be accepted, however, that this arthrophragm represents the fused endosternite and endo- pleurite. It consists of two halves, which are separated in the median line by the posterior end of the median plate. This arthrophragm is practically horizontal, and was designated the “sella turcica” by Milne-Edwards. As already stated, the last arthrophragm fuses in front 880 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. with the dorsal border of the sixth endosternite. Between this arthrophragm and the seventh endopleurite there is a large foramen. Fic, 6—Diagrammatic plan of the endophragmal system to show the muscle chambers. (The corresponding parts are shaded _- similarly throughout). 1—7 = thoracic arthro- phragms 1 to 7. I.P. — VIILP. = pleural muscle chambers of thoracic somites 1—7. ILS. — VII.S. = sternal muscle chambers. of thoracic somites 1—7. VIII.P.S. = pleuro-sternal muscle chambers of last thoracic somite. Hp. = epimeron. i.s. = endosternite. Pl. = endopleurite. St. = sternum. m.=median plate. (2) Anrertor Post-orat EnpopuraGMaL SYsTEM aaeh, we hy (Text fig. 7). This consists of the last three thoracic and the two post-oral cephahe arthrophragms. The nature of the epimera and sterna im this region naturally decides the form and extent of the corresponding arthrophragms. The apparently great differences between the endo- phragmal system of this region and that of the posterior thoracic somites is due to three main causes. aes SEA-FISILERIES LABORATORY. — : 01 (1) There is no median plate. This only begins at the level of the fourth thoracic arthrophragm. (2) The post-oral sterna anterior to the fourth thoracic arthrophragm are all fused together. Con- sequently there can be no broad plate-lke endosternites formed as in growths between the somites. The small endosternite present in each somite of this region is rod- like, and represents merely the articular border of the typical endosternite. (The third thoracic endosternite has the form of a fairly broad and deep plate, and is therefore an exception to this rule.) (3) The epimera in front of the second thoracic arthrophragm are fused together, so that the endopleurite in these somites are extremely reduced and represent only the articular border of the typical endopleurite. Here, as in the posterior thoracic region, each endopleurite gives off a posterior out-growth, which fuses with the following arthrophragm. So that pleural muscle chambers and sternal muscle chambers may be made out, but owing to the rod-like nature of their con- stituent parts, they have a very different appearance from the muscle chambers of the posterior somites of the thorax (see Text fig. 6, also Pl. III, fig. 18). The third thoracic arthrophragm (Text fig. 7, 1.) arises between the third and fourth thoracic somites. Kach endosternite (Pl. III, fig. 18, ¢.sé.8) differs from that of the typical arthrophragm described above. It arises merely from the outer edge of the sternum, so that the two endosternites are separated from each other by the entire width of the sternum in this region. The endosternite is a broad and deep plate facing downwards and backwards. The dorsal and inner corner is prolonged inwards and backwards and almost meets the similar part from the other side. 3382 TRANSACTIONS LIVERPOOL BIOLGGICAL SOCIETY. Eig. 7. A, = anterior view of Ist post-oral cephalic arthrophragm. b.—F. = anterior views of the left side of the following arthrophragm. B. = 2nd post-oral cephalic arthrophragm. C. = Ist thoracic arthrophragm. D, = 2nd thoracic arthrophragm. J. = 3rd thoracic arthrophragm. (The parts are shaded as in Fig. 4). ad. = junction of 2nd cephalic endopleurite with lst thoracic endosternite. b. = point of fusion between 2nd thoracic endosternite and 2nd cephalic endopleurice. c. = line of fusion between 2nd thoracic endopleurite and 3rd thoracic endosternite. d. point of fusion with the Ist thoracic endopleurite. line of fusion between 3rd thoracic endopleurite and the 4th thoracic endosternite. : = line of fusion between 3rd thoracic endosternite and the 2nd thoracic endopleurite. «x. = point of fusion between the 2nd cephalic endopleurite and the 2nd thoracic endosternite. y. = point of fusion with Ist cephalic endopleurite. (The dotted line in Fig. D represents the 3rd thoracic endosternite.) = oh SKA-FISHERI“S LABORATORY. ROO On its anterior face the endosternite is connected with the narrow plate-like second thoracic endopleurite (f.). Near the point of junction of these two plates the dorsal and articular borders are prolonged backwards as rod-shaped pieces, each of which comes into contact with anterior rod-like outgrowths from the corresponding borders of the third thoracic endopleurite. The endopleurite arises betwen the third and fourth epimera. It gives off two short anterior rod-like prolongations from the dorsal and articular borders which fuse with the rod-like extensions of the endosternite mentioned above. The main part of the endopleurite, however, consists of a broad plate, which passes backwards and fuses with the fourth thoracic arthrophragm (e.). Second thoracic arthrophragm (l'ext fig. 7, /). The endosternite is much more reduced than that of the third thoracic arthrophragm. It arises from the upturned edge of the sternum in this somite, and has a very irregular shape. Its inner portion passes upwards, and fuses with a narrow membranous process projecting downwards from the last cephalic endopleurite (0.). The articular border is prolonged outwards as a rod- like process, which fuses with the extremely small articular border of the endopleurite of the same arthro- phragm. About half way along the articular border the endosternite fuses with a posterior rod-like extension of the first thoracic endopleurite (d.). The endopleurite of this arthrophragm is a deep narrow plate arising at the junction of the second and third thoracic epimera. From its lower end it sends forward a short process which fuses with the outer part of the endosternite. The main part of the endopleurite passes backwards and becomes fused with the third thoracic endosternite (C.), as described above. 3384 'TRANSACTLONS LIVERPOOL BLOLOGICAL SOCIETY. First thoracic arthrophragm (‘l’ext fig. 7, U.). The endosternite arises from the upturned edge of the sternum. It consists of a simple rod which passes back- wards, upwards and outwards parallel to the articular border of the second thoracic endosternite. It fuses with the endopleurite of the same arthrophragm, but immediately before doing so it comes into contact, on its anterior side, with a posterior prolongation from the last cephalic endopleurite (a.). The epimera of the first and second thoracic somites are fused together, and the endopleurite of this arthro- phragm arises from the ventral edge of the fused epimera immediately in front of the origin of the second thoracic endopleurite. It is rod-lke, and passes forwards and inwards in precisely the same plane as the first thoracic endosternite, with which it fuses. Near its fusion with the latter, the endopleurite gives rise to a posterior process which fuses with the second thoracic endosternite. Last cephalic arthrophragm (‘Text fig. 7, B.). The endosternites of the two post-oral cephalic arthrophragms are fused together, but there is a distinct longitudinal suture present, which assists in the identification of the two parts.* The fused endosternites pass outwards and backwards parallel to the first thoracic endosternite. After a short distance the last cephalic endosternite becomes distinct from the anterior endosternite, and at the point of separation a prolongation from the first cephalic endopleurite fuses with the endosternites (y.). Vrom this point the posterior endosternite passes outwards and fuses with the lower border of the last cephalic endopleurite. The last cephalic endopleurite is an irregular «There is also a well-marked groove separating the sternum of these two cephalic somites. SEA-FISHERIES LABORATORY. — B00 membranous plate divided into a dorsal and a ventral portion. The dorsal portion has on its inner side a down- wardly projecting process which fuses with the upper part of the second thoracic endosternite (v.) as described above. The ventral portion of the endopleurite has an upper crescent-shaped region and a lower part which fuses with the endosternite. From the posterior side of the lower portion of the endopleurite is given off a rod-hke process which fuses with the first thoracic endosternite. First post-oral cephalic arthrophragm (Text fig. 7, A.). In addition to the portion fused with the last cephalic endosternite, the endosternite of the above arthrophragm has an anterior process at each side which form the skeleton of the metastoma (PI. ITT, fig. 18, met.) or posterior lip of the mouth. ‘The endopleurite arises from the soft membranous epimeron immediately behind the insertion of the external abductor muscle of the mandible. It passes backwards and gives rise to a small upwardly directed process, and afterwards becomes joined to the fused endosternites. INTEGUMENT (Text fig. 8). The crab is covered by a continuous chitinous exoskeleton, which serves partly as a protective covering and also as a means of attachment for the muscles. The main portion of this exoskeleton is strongly calcified. Between the movable somites of the abdomen, however, and also between the articulating segments of the appendages, the exoskeleton remains uncalcified in order to allow of free movement, and has the appearance of a thin chitinous membrane, known as the ‘ arthrodial membrane. ” The exoskeleton of the ventral region of the abdomen a 336 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. is but feebly calcified. The outer walls, the floor and roof of the branchial chamber and the roof of the pre- branchial chamber are also extremely thin and membranous. The chitinous linings of the fore-gut and hind-gut, which are continuous with the exoskeleton, are uncalcified, except in those regions of the fore-gut where the ossicles are present. The gills, also, are covered by an extremely fine chitinous layer. The integument of the crab consists of an epidermis, below which lies the dermis. On the outer side of the epidermis is a chitinous layer, the thickness of which differs considerably in various parts of the body. This outer chitinous layer is a product of the epidermis, and constitutes the exoskeleton already referred to. The chitinous layer may be impregnated with calcareous salts. The epidermis [Chitogenous epithelium, Vitzou*] (Text fig. 8, e.) consists of a single row of columnar cells resting upon a basement membrane (f.). These cells differ in their appearance in various parts of the body, and also show marked changes during the interval between one act of ecdysis and the next. In the dorsal integument of the hard crab, for example, the cells of the epidermis are only moderately columnar, but in the oesophagus of the same animal the cells are extremely elongated. In the soft crabs the cells are of much greater length compara- tively than in the hard crabs. In some regions where we have two parts of the integument coming close together, such as at the edge of the carapace and also the gill lamellae, the cells of the epidermis sometimes become extremely elongated and pass across the dermis to fuse with similar cells from the ** Vitzou, A. N. ‘‘ Recherches sur la structure et la formation des téguments chez les Crustacés Décapodes,”’ Arch, de Zoologie expér, et gém., T. X. [1882], p. 451, 37 6 e LABORATORY. Vitzou has termed such SEA-FISHERIES epidermis of the opposite side. cells “ colonnades de soutien.” 4 a =) o—) rs cab) —_— ee} ao ; = iT x 5 een ering loi, i) S et S vie iN res a = ota seSey | | | yf) ~ eS ee ly of! 7 |/ 3 seaeiiee = yee He - PEEEEPEEEE ane Se 0H =] .| i 6) 5 aon padeaa eRe o ae a == LETT \fovaly- ; Soe BEES eee peed! (1 Dies ee HPRUAERIBEaEiHE | a See a ——— a J on (SSURPGH 88912000 OO ce =e CH He Zaiy\ = © CEE REPE DEE TELE 4 1S ND OOD Pee aa aco OS Gee PURE rete SG] aT Te [| SS Ta TT eee ge) = > VIN CRDHIAREO RT no SSW SB i eae rs MERCURE Sooo See eo monn jon 72) PEAR EER REL ROG Seas Sa Nee ay ae jy ARAL a Sewell — pa SEU 1274 0 OD Ke S) Sane Siaa) o > Se} OE SEG 05225050 5) OC a NM pe ie i | HGPGBGEGRIERSRIECI SWE SSS Tames a= OO REECCEELERCREEEEGED TTT J aa ane TWereceet Pos AVBRDIESITOTBAAed Lea ToS IB ele CEPCEEEEECTCFEP HER | pt HOO Soe o> Be Be L eTOEEPECEELEE RSE, TT i NN JOBE Bi Ey 7 ee a 7G ET EGO mi ee is MeN fie EERE EET LL PL (An os Pe | = » oe eet aos sons eon HON o 9 REET TTT iz li OR elena ov Ae o ot 1 w< Sales o | fe) [om There is uv duct of the cutaneous gland. ment membrane. muscle attached to the base- basement membrane. dermis. g. h. k. f. It consists mainly of a network cutaneous gland. L. uv = non-calcified layer. pigment cells close to the basement membrane. epidermis. The dermis (g.) lies below the basement membrane, = cuticle. b, = pigmented layer. c. = calcified layer. Fic, 8.—Diagrammatic section through the integument of a hard crab. d. é. a. of connective tissue fibres and scattered cells. and varies in thickness. a laver of 338 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. As pointed out by Cuénot,* there are two kinds of cells present in the connective tissue which contain reserve material. These are the “ cellules de Leydig” and the ‘ cellules protéiques.” The former contain glycogen, and are present in great numbers, especially when the period of ecdysis approaches. The latter are also present in ereat abundance, and contain proteid material. The cutaneous glands are also embedded in the dermis. The muscle fibres stretch across the dermis, and are attached to the inner side of the basement membrane. The muscles when dissected appear to be attached to the exoskeleton, but an examination of sections reveals the fact that they do not extend farther than the basement membrane. The chitinous layer of the integument is situated on the outer side of the epidermis, and consists of several layers. Commencing from the outside, these are as follows : — (1) The cuticle (Text fig. 8, a.) is an extremely thin structureless layer covering the whole of the chitinous exoskeleton. Its continuity is interrupted at intervals where the ducts of the cutaneous glands open to the exterior. From the cuticle there arise numerous small papillae, which are only seen when examined under the microscope. ‘These must not be confused with the setae, which are visible to the naked eye and which have an entirely different structure (see below). | (2) The pegmented layer (b.) 1s a moderately-thick layer containing pigment. In the hard parts of the exoskeleton this layer is calcified. It has a laminated structure, and the numerous layers of which this portion of the exoskeleton is composed are parallel to the surface. (3) The calecfied layer (c.) is the broadest layer of all =o Cuenots i, “ £tudes physiologiques sur les Crustacés Déca- podes.”’ Archives de Biologie, T. XIII, p. 245, . SEA-FISHERIES LABORATORY. 339 in the fully-formed exoskeleton. It is colourless and richly impregnated with calcareous salts. Like the previous layer, it exhibits striations parallel to the surface, but the laminae are generally broader than in the pigmented layer. It is to this layer that the great thick- ness and hardness of the shell in a hard crab are due, as new laminae are constantly being added to this region until the exoskeleton attains its maximum thickness. (4) The non-calcified layer (d.) is a very thin layer composed of delicate laminae parallel to the surface. This layer remains in a very soft condition, and is not formed until the calcified layer has attained its maximum width. Vertical sections through the integument reveal the fact that there are striations in the chitin at right angles to the surface, as well as the horizontal lamellae already referred to. Also, as Vitzou has pointed out, in horizontal sections the chitinous integument is divided up into small hexagonal areas, and in each of these areas small pores are present. Vitzou determined that these areas were of the same size and shape as the horizontal sections through the cells of the epidermis. He concluded, therefore, that the exoskeleton is composed of innumerable hexagonal prisms packed side by side, having their long axes at right angles to the surface of the body. Furthermore, each of these chitinous prisms is in contact with the outer end of an epidermal cell. So that for every cell of the epidermis there is a corresponding prism forming a unit of the chitinous exoskeleton. Such an explanation accounts for the presence of the vertical striations in vertical sections, and for the polygonal areas in the horizontal sections. The small pores in the middle of these areas are due to the presence of numerous fine canals traversing each prism from the epidermis to the exterior. ¥ 840 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Mode of Formation of the Exoskeleton. Originally the exoskeleton was believed to be pro- duced by a secretion from the cells of the epidermis. Vitzou, however, claimed that the process is effected in a different manner. According to him the new shell is produced in the following way. ‘The contents of each epidermal cell becomes modified at the outer margin. This outer part becomes cut off from the rest of the cell. Thus at this stage the epidermis is covered by a thin layer, which, however is not one homogeneous whole, but is divided up into numerous polygonal areas, each area corresponding in shape and position to an epidermal cell. The process is repeated; the outer part of each cell is again cut off, and at this stage we have a two-layered polygonal cylinder above each cell. This process is repeated until we have built up over each cell a multi- layered cylinder. Since the cells of the epidermis he close together, the chitinous cylinders are also tightly packed and form what appears to be a continuous exoskeleton. The striations parallel to the surface of the integument represent the successive lines of growth. Thus, according to Vitzou, the process of formation of the chitinous integument consists in the successive thickening of the outer walls of the epidermal cells. Setae. These are long hair-like processes which project from the exoskeleton in various regions of the body. In sections each seta is seen to arise from the region of the epidermis as a narrow tube enclosing a cavity. This tube passes through the chitinous layers and projects from the exterior as a long narrow process. Its walls are cuticular and are continuous with the thin structureless cuticle SEA-FISHERIES LABORATORY. 341 covering the chitinous integument. So that wherever a seta arises the continuity of the thick exoskeleton is broken in order to allow this tube-hke prolongation to reach the exterior. The contents of the setae are proto- plasmic and are connected with the epidermis. In some regions of the body the setae have nerve fibres passing to their interior. These are the sensory setae, of which there are several kinds (see section on Sense Organs). The setae may be simple prolongations, or they may consist of a central axis, from which arise off-shoots. In the latter case the cavity of the central axis is not continued into the lateral out-growths. In addition to the setae described above, there are small papillae on the surface of the shell, which are merely thickenings of the cuticle and do not contain a cavity. Vitzou states that in Portunus these cuticular processes are comparatively long. In Cancer, however, they are extremely small, and can only be detected under the microscope. Vitzou affirms that the long “ setae,’ present in the walls of the fore-gut, have no central cavity, and are probably merely extremely large cuticular prolongations and not true setae. ‘ These “setae”? in the fore-gut act as strainers. Where the sub-branchial region of the carapace is closely applied to the bases of the thoracic legs there is a rich growth of setae. These probably assist in preventing the water from entering the branchial chamber at the base of the thoracic legs. The inhalent branchial opening is also well guarded by long setae, both on the flabellum of the third maxilli- pede and on the anterior border of the coxopodite of the chela. The setae on the endopodites of the pleopods in the female are used for the attachment of the eggs. 842 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Cutaneous (or tegumentary) glands. Scattered throughout the connective tissue, near the basement membrane, are globular masses of cells, each cellular clump being connected with the exterior by a fine duct. These are the cutaneous glands. Each cell of the globular mass is in contact with a small cavity on its inner side. This central cavity of the glandular mass receives the secretion from the various cells. The cavity is connected with the duct, and thus the glandular secretion is enabled to pass to the exterior. The duct is lined by a fine protoplasmic wall. The wall of the duct probably represents a single cell, in which case the cavity of the duct is intracellular. The gland cells and the duct cell are all modified epidermal cells. The cutaneous glands are scattered throughout the integument, and in some regions are extraordinarily abundant. The glands present in the mandibles and in the walls of the oesophagus, and also those in the hind- gut, have a similar structure to the ordinary glands on the surface of the body. They are, in fact, modified cutaneous tegumentary glands. Immediately in front of the mouth there is a compact mass of cutaneous glands at each side, which open on the surface of the epistoma. These glands have the structure of the typical cutaneous glands, but are extremely large. They are about four times as large as those present in the walls of the oesophagus (see section on Alimentary Canal). Similar glands are found also in the metastoma, packed very closely together. Herrick” has also observed them in the same regions in the lobster. (See fig. 60.) In the floor of the branchial chamber there is a well- defined transverse ridge lying in front of the inhalent * Herrick. ‘‘The American Lobster.’’? Bull. U.S. Fish Com, Vol. XV., 1895, SEA-FISHERIES LABORATORY. 343 branchial aperture. The epidermis in this region presents a very interesting condition, and there appear to be numerous modified cutaneous glands. There are also great numbers of cutaneous glands present on the endopodites of all the maxillipedes. On the endopodites of the pleopods of the female there are closely-packed tegumentary glands. According to Herrick, these secrete the cement which attaches the eggs to the endopodites of the abdominal appendages. The function of the various tegumentary glands in various parts of the body is not clearly known. lLang* states that some have an excretory function. There is httle doubt that the functions of these glands differ in various regions of the body. Those, for example, on the pleopods are extremely specialised. It is not incon- ceivable that the glands in the integument of the epistoma and metastoma may produce a secretion which is poured on the food as it enters the mouth. The glands in the walls of the oesophagus are probably salivary glands. Herrick thinks that this explanation of their function no longer holds good, since glands of similar structure have been found in the walls of the hind-gut. This argument, however, does not carry much weight, if we recognise that all the tegumentary glands (both on the surface and in the walls of the alimentary canal) have the same essential structure, and yet are capable of performing different functions in various regions of the body. Kcpysis. The epidermis of all Arthropods is covered by a continuous layer of chitinous integument, which may become calcified in certain regions. This outer integu- *Lang. Text-book of Comparative Anatomy, Part I. 844 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. ment is continuous with the chitinous lining of the fore- gut and hind-gut. The body, therefore, may be said. to be enclosed in an inflexible coat, which prevents the tissues from expanding. The growth of the animal cannot be gradual, but can only take place when the animal breaks through the stiff outer covering. Immediately after exuviation, the animal, which is then only covered by an extremely thin flexible membrane, will increase in size. ‘This process of casting, or ecdysis, is characteristic of all Arthropods. Lcdysis takes place periodically, and growth can only take place while the animal is in a “soft ’’ condition. In Cancer, when ecdysis is about to take place, the carapace opens along the pleural groove at each side. These two longitudinal splits become connected posteriorly with a transverse opening, which makes its appearance between the posterior border of the carapace and the tergum of the first abdominal somite. Thus the tergal region of the carapace is free from the remainder of the exoskeleton, except along a lne marking the posterior boundary of the first cephalic sternum. ‘The carapace, therefore, acts like a hd of a box, and 1s hinged anteriorly. The first part of the body to be withdrawn from the old shell is the abdomen, which is followed by the various legs. When all the parts are completely. free the crab emerges from beneath the hinged carapace. On the dorsal sides of the basi-ischium and meros of the chela there are faint grooves (Pl. I, fig. 12, abs.). These are the “lines of absorption,” and at the time of ecdysis the exoskeleton of the chela loses its calcification at these points. In this way the withdrawal of the large claw is effected, as it would be extremely difficult for the chela to be withdrawn if the integument at the base of the limb remained hard. all SEA-FISHERIES LABORATORY. 845 As pointed out by Vitzou,* the method of ecdysis in the Macrura differs from that found in the Brachyura, because in the latter the abdomen is withdrawn first. In the Macrura the thorax is first withdrawn, and the abdomen leaves the old shell last. The tissues of the animal become greatly changed immediately before ecdysis. The blood increases enormously in volume, and Wittent suggested that the increase is due to the absorption of water by means of the — digestive gland. He presumed that this excess of blood plasma produced the internal pressure necessary for ecdysis and growth. The muscles become very soft and semi-fluid, and the fibres lose their well-defined outlines and cross-striations. | The digestive gland probably increases in size during ecdysis. The fat cells are stocked with glycogen, the ferment cells are much bigger, and the colour of the ferment vesicle is of a deep brown colour, thus giving the digestive gland a deeper colour at this period. The reproductive organs are generally in an immature condition at the time of ecdysis. Immediately before and after ecdysis the crabs are unfit for food. They are ‘“ watery” and have a bitter taste. Reference is made in the Economie section to the ’ erabs, which are considered by the fishermen to be diseased crabs. I have reason to believe that they “Granny ’ are merely crabs preparing for ecdysis. . One of the most interesting changes which accom- pany ecdysis is probably the formation of the new integu- ment, as a result of the extreme activity of the epidermal cells. This new exoskeleton is already formed when the hard shell is discarded. * Vitzou. Arch. Zool. exp. et gén., T. X, 1882. + Report on the Scientific Investigations, Northumberland Sea- Fisheries Committee, 1903. 346 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Before ecdysis the cells of the epidermis become greatly elongated, and in the underlying dermis the cells of Leydig, which are rich in glycogen, become extremely numerous. The supply of reserve food material in these cells is evidently of the utmost importance at a time when erowth and regeneration of the tissues is taking place. At the time when the crab is preparing to cast, a new chitinous layer is formed by the epidermis. This new layer 1s separated from the old shell by a gelatinous fluid. The chitinous layer, which is the first appearance of the new exoskeleton, consists of two parts—an outer structureless cuticular layer, and an inner chitinous layer containing pigment. This inner layer represents the pigmented layer. The calcified and non-calcified layers are not produced until after ecdysis. he calcified layer grows throughout the greater part of the period until the next ecdysis, and it is to this layer that the hardness and increasing thickness of the shell is due. Vitzou’s theory explaining the method of formation of the exoskeleton has been described’ above (see section on Integument). The frequency of casting and other problems connected with ecdysis are discussed below in the section on Economics. | AUTOTOMY AND REGENERATION OF LIMBs. One of the most interesting and characteristic features in the natural history of the crab is the power the animal possesses of throwing off injured limbs (autotomy) and of forming new limbs to replace the old (regeneration). The processes associated with these phenomena may be briefly stated as follows :— If the distal portion of one of the pereiopods be SEA-FISHERIES LABORATORY. 347 seriously injured, the crab immediately throws off part of the Lmb. The whole limb is not sacrificed. The self- amputation always takes place along the thin groove present on the basi-ischium representing the line of separation between the basipodite and ischiopodite. This _ groove, therefore, may be said to surround the fracture plane (PI. II, fig. 12, f.p.). When autotomy has been effected, the fracture plane is seen to be covered by a thin membrane, or diaphragm, which is perforated, shghtly below the centre, by a small foramen. The blood flows out through this small opening, but soon coagulates, forming a clot over the mouth of the foramen and also on the outer surface of the diaphragm. The diaphragm with its outer coating of coagulated blood assumes a dark brown colour in a few days, and ultimately becomes quite black. This black coating 1s worn away in course of time, and reveals a thin membrane extending across the stump. Beneath the membrane a small papilla makes its appearance, and marks the commencement of the regeneration of the limb.” Conditions necessary for Autotomy. The successful performance of self-amputation in Cancer depends upon several conditions, of which the most important are discussed below. 1. The crab must be healthy. This is a most important factor. Animals which are in a diseased or weak condition, or which have been kept out of water for a considerable time, and in which, as a * According to Williamson, the regeneration only takes place when the crab is preparing for ecdysis. The limb does not attain its full size at the first moult after regeneration. Two or three moulting processes must take place before the limb attains its normal size. 348 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. consequence, the nerve responses are feeble, do not perform autotomy very readily. 2. The nerve of the limb must be sufficiently stimulated. This appears to be a self-evident proposition. What- ever may be the cause of autotomy, and whatever may be the reason of this complex phenomenon, it is without doubt the result of nervous stimulation. But the question as to what is a “ sufficient ” stimulation cannot be disposed of so easily (see below under the general discussion on Autotomy). 3. The thoracic nerve mass must remain intact. We are indebted to Fredericq* for his investigations on the physiological processes involved in autotomy. He has proved that the latter is the result of a reflex, and that the thoracic ganglhon belonging to the appendage is the centre of this reflex. The brain is the seat of voluntary and co-ordinated movement in Cancer, and if the brain be removed autotomy will still take place. If, on the other hand, the thoracic nerve mass be removed or destroyed, self-amputation cannot proceed. The afferent nerve fibres which are stimulated as the result of injury to the limb are connected with the ganglion cells of the thoracic nerve mass, and from these the efferent fibres pass to the extensor muscle of the basi-ischium. This muscle is the one concerned in the autotomy, and thus we are provided with a fourth condition. 4. The integrity of the extensor muscle of the basi-ischiwm must be maintained. The first movement after the limb has been injured is the extension of the basi-ischium; i.e., it moves in a dorsal direction. This movement continues until the *Fredericq, L. ‘‘ Nouvelles recherches sur l’autotomie chez le crabe.”’ Archives de Biologie, T. XII, 1892. SEA-FISHERIES LABORATORY. 349 distal portion of the limb comes into contact with the carapace or with some other fixed object, when the limb breaks at the fracture plane. That this upward move- ment, or extension, of the basi-ischium is necessary for autotomy may be proved by cutting the extensor muscle (or muscles), and then injuring the hmb. No self- amputation will then take place. If the flexor muscle be cut, and the extensor remain uninjured, autotomy will proceed. 5. The distal portion of the limb must come into contact with some pont of resistance. This condition has been emphasised above. As soon as that part of the hmb on the distal side of the fracture plane comes into contact with some point of resistance (e.g., the carapace) the upward movement of this portion is stopped. The proximal portion of the basi-ischium, however, still continues to move upwards under the influence of the extensor muscle. Thus there are two forces acting on the fused basi-ischium—a force at the proximal end tending to move the segment upward, and a force at the distal extremity preventing this upward movement. A great strain is produced on the basi- ischium and it snaps at its weakest point, which is the fracture plane. 6. The stunulation to produce autotomy must be applied between the fracture plane and the distal end of the propodite. The nerve does not pass into the dactylopodite, so that if the latter segment be wounded the nerve will not be stimulated. It is equally futile if the lmb be damaged on the proximal side of the fracture plane. ae 350 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Amongst the Brachyura two kinds of autotomy have been recognised. (1) If the crab is captured by means of one of its limbs it will throw off the hmb in order to escape from its enemy (“evasive autotomy ”). It is evident that all Decapods do not act similarly under such conditions. It does not appear to be the case in Cancer or Carcinus. Fredericq’s researches led him to believe that crabs did not throw off legs in order to escape from enemies, but his experiments were confined to a few species. ‘Taking all the evidence available, it would appear that autotomy does take place under the above conditions in some crabs, such as the Matidae and the Grapsidae. (2) Lf one of the legs of a crab be severely wounded, the limb will be thrown off. This probably occurs without exception in the Brachyura. It is well to remember that in both cases we are probably dealing with essentially similar physiological conditions. In both cases the autotomy is produced as the result of the stimulation of the nerve of the leg, and the difference appears rather to be one of degree than of kind. In both the above cases the autotomy is produced as the result of a reflex, and the seat of this reflex is in the ganglion of the somite to which the autotomised leg belongs. Quite recently, Piéron* has concluded that there is still another kind of autotomy which is purely voluntary, and will not take place after the commissures connecting the cerebral ganglia with the thoracic mass have been cut. One of his experiments with Grapsus was as follows :—A leg of the crab was tied to a stake within view of a * Piéron, H. C.R. Soc. Biol., 11th May, 1907. Jbid., T. XTi (1907), Nos. 33 and 34. SEA-FISHERIES LABORATORY. B51 sheltered crevice in the rocks. The crab discarded the imprisoned limb as a conscious effort in order to reach the inviting shelter. This did not happen if the brain were destroyed or if the commissures were cut (‘‘ psychic autotomy ”’). lt is difficult at the present juncture to accept Piéron’s explanation, as Mlle. Drzewinat has also per- formed similar experiments with Grapsus, and_ has obtained entirely different results. But so far as Cancer is concerned, the ‘ psychic autotomy ” does not appear to be present. : It is not possible in the present state of our knowledge to arrive at a definite conclusion with regard to the full significance of the processes involved in autotomy. But whatever may have been the lines along which autotomy has been evolved, there is no doubt that one of its most important objects is the prevention of bleeding. If the arthrodial membrane between an appendage and the body be cut, the crab will probably bleed to death, and this appears to be one of the greatest dangers with which the animal has to contend. The limbs, on account of their position and size, are continually in danger of being torn or crushed. If the limb were seriously injured, and autotomy did not take place, the crab would bleed to death, because the wounded surface would probably be too large to allow coagulation to take place. This difficulty is surmounted by the hmb being thrown off at the fracture plane, across which, as we have already seen, a membrane is stretched. ‘This membrane is perforated by a small foramen through which pass the nerve and blood streams connecting the proximal and distal parts of the appendage. Over this foramen a clot may readily be formed, and thus the excessive bleeding may be prevented. + Drzewina, A. C.R. Soc. Biol., T. LXIII (1907), Nos. 33 and 34, 352 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. ~ Histology. (Text fig. 9). Before autotomy. A longitudinal section through the basi-ischium of a pereiopod in which autotomy has not been effected displays the following structure (94A.). In the region of the fracture plane the exoskeleton is discontinuous, the plane of the discontinuity being at right angles to the longitudinal axis of the basi-ischium. The break is not always easily detected, as the two parts fit very closely together. On the inner side of the exoskeleton is the normal layer of epidermis (ep.). At the plane of breaking the epidermis turns inward both at the distal extremity of the basipoditic region and also at the proximal end of the ischiopodite. These ingrowths extend as far as the central nerve and blood vessels, where the epidermal ingrowth of the basipodite (z.) becomes continuous with that of the ischiopodite (0.). In other words, across the plane of fracture the epidermis underlying the exo- skeleton is not directly continuous, but becomes turned inward as far as the central nerve of the leg. Thus there is a double diaphragm stretching across the leg in the fracture plane, and near the centre of this double membrane there is a small opening which permits of the passage of the nerve (n.) and blood vessels from one side to the other. The walls of this narrow opening are composed of a cellular membrane, which connects the proximal and the distal diaphragms. After autotomy. The ischial portion of the exo- skeleton is broken away at the fracture plane, and the underlying structures belonging to the ischium have also been torn away. ‘These include the epidermis of the ischium and also the distal portion of the diaphragm. Stretching across the broken end of the stump (Text SEA-FISHERIES LABORATORY. 353 B.) is a membrane representing the proximal of the double diaphragm (7.). Near the centre sa small foramen. In sections taken immediately totomy there is a layer of coagulated blood (b.) puter side of the diaphragm. e torn edge of the diaphragm in contact with the appears to grow over the latter. Thus, shortly e autotomy has been effected, there 1s a continuous ne or diaphragm covering the broken stump This membrane 1s composed of a single layer of val cells, which is continuous with the epidermis ing the exoskeleton of the basipodite. On the de of the membrane is a layer of coagulated blood. inner side of the ectoderm of this membrane, and lose to it, there appears to be a continuous layer of lve tissue fibres. Miss Reed* describes also the of a dense mass of blood cells immediately 2 the membrane. generative process. Shortly after autotomy has ace the cells of the diaphragm begin to degenerate ig. 9, D.). Ultimately there is on the outside of the a layer of dead tissue, formed of an outer layer of ated blood, beneath which is the layer of degenerate mal cells. According to Miss Reed, there is also er layer of degenerate blood cells. The dead mal cells of the diaphragm become disconnected he epidermis underlying the exoskeleton of the und this epidermis grows inward beneath the dead ayer. ‘This takes place from all sides, and the wing cells meet in the centre and form a single nfortunately I did not have access to Miss Reed's paper on stological processes in connection with autotomy until after my bservations had been made. My results, in the main, however, ut the conclusions arrived at in her paper (Bryn Mawr College raphs, Reprint Series, Vol. V, 1905). 354 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIE a8 [oonIss San aad oe one “0 ° Stee a 1, , . : B | ~P | OS eT * Ooo Osc p ret pry PS BOGOGODCUODDDOUNUREuuUUODD! Fic. 9.—Diagrams to illustrate the histology of the structures im the fracture plane before and after autotomy. (In all the diagrams the proximal end of the limb is to the left). A. = longitudinal section through basi-ischium before autotomy, showing the double nature of the diaphragm. B. = longitudinal section through the basipodite immediately after autotomy. Showing the single diaphragm and the foramen. C. = longitudinal section through the basipodite shortly after | autotomy. The epidermis of the diaphragm has grown over the foramen. D. = the degeneration of the diaphragm and the formation of a TRWAr ae oy layer of epidermis beneath. ay ge H. = Formation of a thin cuticle (which is continuous with ‘the: ae exoskeleton) by the new epidermis. > ep. = epidermis. nm. = nerve of the appendage. so 4 ex. = exoskeleton. b. = coagulated blood. #3) seams a. = proximal part of diaphragm. d. = degenerated diaphragm Bs 3 o. = distal part of diaphragm. and blood tissue. Bes Be ep’. = new epidermis. cut. = new cuticle formed by the | 2 ‘ 4 new epidermis. — * jue “a SEA-FISHERIES LABORATORY. 300 layer of cells beneath the outer dead layer. Eventually a thin layer of chitin is secreted on the outer side of these cells (Text fig. 9, #.), and this layer of chitin is continuous with the exoskeleton. The old membrane, which is now almost black, becomes worn off, and this new chitinous membrane is exposed. The cells in the new layer of epidermis become xxtremely active, and increase in number internally. At first an undifferentiated mass of cells is formed beneath the membrane, but gradually differentiation takes place and the new parts of the limb are laid down in miniature. As they increase in size they grow outward, and form a small papilla on the stump. MUSCULAR SYSTEM. (Pls. III, IV). Muscles OF THE CEPILALOTHORAX. I. Eye. The ocular peduncle consists of two parts —an inner rod-like portion extending inwards as far as ihe middle line, and an outer swollen portion at the free end of which is the visual organ. The outer portion articulates with the inner, and is connected with the latter by means of a flexible membrane. The movement of the outer portion is effected by two small muscles—a ventral flexor and a dorsal extensor. Il. First antenna. The muscles are extremely small. The basal segment of the protopodite has a dorsal extensor and a ventral flexor. In their natural condition the second and third segments are flexed. In both cases the extensor 1s on the inner side and the flexor muscle is on the outer side. Z 356 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Ill. Second antenna. The basal region of this appendage is fused with the carapace, and the muscles. have degenerated. The operculum, which probably represents the coxopodite, is still freely movable, but its extensor and flexor muscles have now another function in connection with the raising and closing of the operculum. The whole question of the homology of the opercular flagellum has not much movement, and its muscles are muscles has been fully discussed by Marchal.* The j very small. IV. Mandible (fig. 31).. There are two sets of muscles—the adductors for closing the mandibles and the abductors for opening the mandibles. Eaternal adductor muscle (e.a.md.). Arises as a broad band from the anterior and outer portion of the sub- hepatic region of the carapace. It passes inwards and upwards, and is inserted on a long tendon attached to the outer part of the mandibular apophysis. Internal adductor muscle (v.a. md.). Arises from the urogastric region of the carapace. It passes downwards and forwards as a short broad muscle, and is inserted on an extremely long narrow tendon attached to the posterior margin of the mandible. Haternal abductor muscle (e.b. md.). Arises from the posterior and inner corner of the hepatic region of the carapace. It passes directly downwards, and is inserted on a narrow tendon attached to the posterior side of the apophysis. ‘This muscle is comparatively small. Internal abductor muscle (2.b. md.). Arises from the top of the vertical rod-like portion of the first post-oral endopleurite. It passes outwards and forwards, and is attached to the outer part of the apophysis. : * Marchal. ‘‘ Appareil excréteur des Crustacés Décapodes.’’ Archives Zool. exp. et gén. (Ser. 2), T. X, 1892. SEA-FISHERIES LABORATORY, ay Me -Forst maxilla. (fig. 26):0 There are two extensors and two flexors. Flevors. One outer (0.e.m.) and one imner (t.e.m.) muscle, which run together and arise from the outer portion of the protogastric region df the carapace. They pass directly downwards together, and when near the maxilla the two separate and are inserted on the outer and inner parts of the coxopodite respectively. Katensors. One outer (0.f.m.) and one inner (t.f.im.) The tops of the two pillar-lke portions of the first post- oral endopleurites are joined by a strand of tissue. Beneath the arch thus formed the two muscles arise near the middle line. They pass downwards and _ slightly inwards, diverging somewhat as they approach the appendage. ‘hey are inserted on the coxopodite at the same point as the corresponding flexor muscle. VI. Second maxilla. There are two extensors and two flexors. Eatensors. The inner extensor arises from the posterior face of the first post-oral endopleurite. It is a short muscle which passes downwards and _- slightly outwards, and is inserted on the outer side of the coxo- podite. The outer extensor is a long narrow muscle. It arises from the epimeron of this somite just in front of the last cephalic endopleurite. It passes inwards and down- wards across the anterior face of the flexors of the scaphognathite, and is inserted close to the small inner extensor. The two flexors are small, and arise close together near to the origin of the outer extensor. They pass directly downwards, and are inserted near together on the inner side of the coxopodite. 358 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. The Scaphognathite (figs. 27, 28) has a complex movement, and the plane of motion is roughly at right angles to its long axis. ‘There are two sets of muscles— extensors which pull the organ downwards, and flexors which draw it up again to its natural position. In the upward movement the scaphognathite does not remain flat, as when in a position of rest, but it becomes curved so that the upper side is concave. This is effected by a set of accessory muscles. The latter extend into the leaf-like portion of the scaphognathite, and do not stop at the edge of the organ, as do the other muscles. All the flexors arise from the anterior face of the last cephalic endopleurite. Their names have been given according to the position of insertion on the scapho- enathite. The flexors are inserted on the anterior wall of the base of the scaphognathite. Inner flexor (i.e.s.) A long narrow muscle arising from the upper part of the endopleurite. It passes down the latter and, turning slightly inwards; it is inserted on the innermost part of the base of the scapho- gnathite. It has a small branch which arises from the side of the epimeron. Outer flexor (o.¢.s.) An extremely broad muscle, which arises immediately beneath the origin of the previous muscle and also on its inner side. It passes down the endopleurite parallel to the epimeron, and is inserted on the extreme outer edge of the base of the scaphognathite. Outer median flecor (o.m.e.) and then over the passes over the “accumulator pulley ’ recording apparatus on deck to the winch. When all is in readiness, word is given to lower the net. An assistant should note the moment that the mouth of the net reaches the surface of the water, and shout a word of warning. This is the zero, and at this moment another assistant who is observing the recording meter takes down the figures exposed. To these figures the required depth should be added, and then the net can be lowered until the meter gives the necessary numbers. When the net has been hauled again to the surface, it is held over the ship’s side and well washed down with a strong stream of water. This is most important, as a great quantity of the catch is often lodged under the mouth-piece lower ring. A strong stream of salt water from the hose is by far the best method of washing the catch down into the filtering bucket, and if no steam hose is available, a small hand pump worked on the deck is better than using buckets. A separate filtrator is un- necessary. After the net has been well washed and the water allowed to run out until only a little remains in the bucket, this 1s unscrewed and the catch can now be removed and fixed. PRESERVATION OF THE CATCH. When preserving the catch it is advisable to remove as much sea water as possible, and to use a reagent that will be simple in applecation and render the organisms easy of identification. For this purpose 90 per cent. of alcohol is used directly, it having proved the most con- venient for ordinary purposes in quantitative work. It METHODS OF PLANKTON RESEARCH. 513 is applied as follows:—The filtering bucket which has been unscrewed from the net is inclined so that what little water remains in it lies over the silk. By carefully tapping or rubbing the latter, this water can be got rid of; but in dog this great care must be taken that the water, and consequently part of the catch, does not run over the edge of the bucket. The filtering bucket is now held over a glass tube or bottle, the tap opened, and the whole catch washed out by a strong stream of alcohol directed from a wash bottle directly on to the organisms on the znside of the bucket. By this means the catch is easily removed by the fixing fluid itself, the sea water is reduced to a minimum, and the catch is fixed and put in its preserving fluid as soon as possible after leaving the water, by means of one operation. The bottles can be stored away and taken to land for further investigation. To run the contents of the filtering bucket into salt water and carry to land 1s, even when only an hour intervenes, not at all advisable and, of course, impossible on a long cruise. THe EstTIMATION OF THE CATCH. There are two methods at present in use by which the plankton tables are constructed. One is a simple method of estimation by examining the catch under the microscope, noting down the forms that occur and denoting their frequency by letters such as ¢.c. (very common), ¢. (common), + (neither common nor rare), r. (rare), r. 7. (very rare). This method is still the most general one in use. ‘The other method is that carried out by the Hensen School, and forms as essential a part of the quantitative work as the nets themselves. By this latter, the actual organisms present in a known fraction of the catch are counted. Since the first method still is 514. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. the most common, it will be necessary here to emphasise its great defects and almost worthlessness for quantitative work when not supplemented by the other. Suppose that one has a certain plankton catch obtained by a vertical haul of the net through 40 fathoms, that the catch has been estimated, and according as the various forms are relatively frequent or rare, they have been designated with letters as above described in the tables. Now we will assume that a second catch taken in another place from the same depth has all the organisms present in the same relative proportions as in the first, but in double or treble the quantity. This would make no difference whatever in the tables, the relative frequencies still remain the same, even though a form which is represented by “rare” in both catches may be present two, three, or four times as many in one catch as in the other. Thus the tables could not be directly comparable for quantitative purposes. We have, however, assumed here that the constitution of both catches was identical a thing of almost impossible occurrence. Let us assume now that the constitution varies, and that three catches are taken (an example given by Apstein), as one takes a voyage out from the coast, and that these are estimated by both methods. By counting, the first is found to contain 50,000 Ceratiwm fusus and great masses of the diatom Sceletonema. In the second catch, taken further out, there are still 50,000 C. fusus, but the diatoms have disappeared. At the third station C. fusus still remains at about the same number, but Ceratewm macroceros, up till now rare in the catches, appears rather abundantly. Now, an investigator who simply estimated the relative frequency of these organisms would state that C. fusus was very rare in the first catch (since they were over- shadowed by the great masses of diatoms), common in METHODS OF PLANKTON RESEARCH. 515 the second catch (where in proportion to the diatoms and other forms they seemed abundant), and again very rare in the third catch (where the C. macroceros has appeared so abundantly). In reality, however, the number of C. fusus has remained the same. An observer estimating by relative frequencies would have constructed a table and curve showing a great increase at Station 2, and then sought for an explanation of this increase, which in reality did not exist. If plankton tables are to be con- structed for a large sea area, in order to compare the plankton at different places under different conditions of salt contents, temperature, currents, and other changing conditions in the sea, guete false results would be obtained from the method of estimation without counting. Moreover, the reliability of such estimations is not good. In order to determine this, Apstein and one of his colleagues took four catches and first simply estimated them in the usual way, and then counted and estimated by the Hensen method (14). A section of the table will show the results. The first column gives Apstein’s estimate, the second gives that of his colleague, and the third gives the true number present as found by counting the various forms present and then using letters derived from the frequencies determined by the counting, in order to compare with the other two columns. By Ac Dy: R., by counting estimation. estimation. method. Rhizosolenia alata ......0...+0+0s rf + 77 e Ssemispina .:....... a 1B ge - shrubsolei ........ Cc Cc 53 stolterfothi ...... r r + S styliformis ...... + + Cc Ceram: WIPOS »«...sc0c000r-02 =. cc cc c ss WOUISIPES -sonees deems cleiss cc + cc Pe LOECAY see ons cask iocxes “b © cc a POUBUG. Sie wan dieer aren xe ie r + CYPUCWAMbeS. sbi ictsscceboesses r r LUTHIT S215 a ee ee r + Cc MoMTSeAN TAEVAGC... ccccensscectees + + Cc CEMOMICUE ie ri) cddesivesscntaarsesds Cc Cc KK 516 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. Kighty-one species were estimated in the catches, and in only one case did both estimations agree with the numbering. It was possible for three things to happen: (1) For both estimations to agree with the numbering; (2) for estimation and numbering to give parallel results, but not be alike; (3) for estimation and numbering to be contrary to one another. Only one species agreed in every respect, 13 species gave parallel figures, and in 67 species the estimations and numbering were contrary. Thus the personal error forms an additional source of failure in the simple method of estimating a catch by the frequencies, whereas by the counting method two observers will practically agree, if both count the same catch. Thus, for tables to be of any scientific worth in comparisons made to show the dependency on hydro- graphical or other conditions, or of the various forms upon each other, the catches must be made quantitatively and the unfortunately tedious method of counting followed. A very detailed account of the apparatus and method of counting has been given by Jenkins (12), but the . method as at present carried out for general work will be briefly described here, in order to give the complete. procedure. The first work consists in the estimation of the volume and the construction of curves to illustrate this. In most cases, unless the plankton is caught on an expedition lasting some months, the volume estimation will be made on shore. If it is required to estimate the volumes of the catches on board ship, the usual swinging table is required. ‘The catch which has been fixed and preserved in alcohol is allowed to stand, and the alcohol decanted and its place taken by distilled water. The catch in distilled water is now brought into the measuring vessel. If distilled water is not used instead of the METHODS OF PLANKTON RESEARCII. 517 alcohol, the volume will be quite inaccurate, because a precipitate forms from the salt water that has been round the organisms when first fixed. This in appearance 1s hke a diatom deposit, and the volume of a catch may be reduced to one-third by transferring from alcohol to water, owing to the removal of this precipitate. Ordinary measuring glasses are of no use for measuring accurately small catches. A special make of glass tube is used, the bottom of which is drawn out into a cone ending in a blunt point, so that a small volume of catch will occupy a considerable depth of this narrow termination. ‘The plankton catches in distilled water are transferred to these tubes and allowed to settle for 24 hours. A mark is then made with ink on the outside of the tube at the level to which the sediment attains, and the catch is again removed. The quantity of water measured out by means of a burette, which takes up the same space as the sediment, will be the volume of the catch. This volume estimation is necessarily very rough, since, especially if diatoms be present, a quantity of liquid remains between the organisms and causes the sedi- ment to appear much greater in volume than it really is. Having found the volume of the plankton in cubic centimetres, it is multiplied by 80 (for the Middle Apstein Net pulled up } metre in 1 second), and this gives the volume present in a column whose area is one square metre and whose length is the distance through which the net has been hauled. For purposes of comparison and the making of curves, the average volume per cubic metre is generally reckoned from the above. The next division of the work consists of counting the organisms. For general use with the Middle Net the catch is brought into 50 c.cm. of distilled water. If the catch is very large a further dilution may be neces- 518 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. sary. This 50 c.cm. with the catch is placed in a shaking flask, and, by means of the plankton pipettes, 0-1 c.em. of the fluid is withdrawn after carefully distributing the organisms by thorough shaking. Tt is necessary here to emphasise the use of these special pipettes devised by Il[ensen (1 and 5), since no other apparatus will allow of the accurate abstraction of such small quantities. First, 0'1 c.em. is taken and removed to the counting plate under the microscope, and the organisms counted. A sheet of paper is used with the names of the species to be counted, and, as each form is passed over, a stroke is placed opposite the name on the paper. Since 0°1 c.cm. is <5 of the 50 c.cm. to which the catch was diluted, the numbers must be multiplied by 500 to give the full number for the catch, and then from this the number per cubic metre is calculated. In general use only one plate is counted with O°'1 c.cm., and then a _ pipette abstracting 0°2 c.cm. is used in the same way, but only those organisms occurring in very small numbers, or doubtful in the first plate, are counted in the second, so that whereas 50 species may be counted in the 0'1 c.cm., this number may be reduced to 12 in the 0:2 c.cm. Following these two plates, 0°5 c.cm. and then 1 c.cm, are taken, and finally the rest of the catch for the larger forms and for rare forms is counted, making a total of five plates. When greater accuracy is required, more plates are counted for the same pipette until the difference between the number of organisms on the last counted and the average number for the previous plates is less than 5 per cent. If an organism is required for a preparation or for further observation, it can be removed from the numbering plates by very small capillary pipettes about two inches long. MELHODS OF PLANKTON RESEARCH. 519 During the last few years it has become obvious that the catch with the fine meshed bolting silk only gives an incomplete sample of the plankton present in the sea at any given place. Kofoid (8) and Lohmann (11, 13 and 18) have both emphasised this error, but it is to the latter that we are indebted for a complete investigation of it and of the means of overcoming any failings in this direction. In an important paper, published in 1902, an account of the comparisons between various methods for catching the smaller plankton organisms was given in detail. The subject has since that time been further investigated, and whilst writing this a detailed and very elaborate account, bringing the plankton work up to date, is going through the press (18). By the kindness of Prof. Lohmann, I have been able to see his tables and read through the proofs of this work. Hensen’s method rests on two hypotheses :—(1) That the pelagic organisms in the sea inside a region of like conditions of earstence, with regard to time and space, are so equally distributed that by the investigation of relatively small quantities of water, a sufficiently accurate picture of the quantity and quality of the plankton for the whole region can be obtained. (2) That the apparatus used for these investi- gations, namely, the Hensen net, even with its uncon- trollable errors, gave essentially a true estimate of the plankton. The first hypothesis will be discussed later. With regard to the second, there is the possibility of the net failing to catch an important part of the plankton, through small organisms passing through the meshes. Hensen himself in 1887 stated (1) that if he allowed the water filtering through the silk net to pass through close silk, filter paper, &c., and investigated the residue, many diatoms, peridinians and silicoflagellates would be found to have passed through the net. He believed, however, 520 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. that the influence of this loss, on the constitution of the catches and the results given by numbering, was of no essential importance, since the mass of the forms slipping through was only small in comparison to the quantities caught by the bolting silk; and, in any case, Hensen gave his numbers as a minimal value, recognising that a loss must occur. Kofoid in 1897 (8) through new investiga- tions in the fresh waters of North America came to the conclusion that the loss which enters into the results, when nets of “ Millergaze”’ are used, was much greater than Hensen had supposed. By using filters of hardened paper, he demonstrated that only 2-50 per cent. of the organisms were caught by the net. Lohmann (13), when investigating the Appendicularia, also found that the quantity of small forms going through the net must be of far greater importance than was formerly supposed. Nothing shows the loss more distinctly that the investiga- tion of the food of the plankton organisms themselves. One finds in their alimentary canal the remains of the smallest diatoms, Peridinians, Coccolithophoridae and Silicoflagellates, of which an ordinary net used in the same water in which the “devourers” (Pteropods and Appendicularia, &c.), lived, would contain none or few. As showing the importance of this loss, Lohmann mentions the fact that the Coccolithophoridae, which play a great part as food for the plankton animals of the North Sea, are almost unrecorded in the tables when bolting silk nets are used. The most favourable organism on which to study the food of the plankton animal is the Appendicularian, which does not take food directly into the alimentary canal, but secretes a special structure, the “house,” for the purpose of catching its food. This is a perfectly transparent structure, and under the microscope can be METHODS OF PLANKTON RESEARCH. 521 seen to contain the uninjured and living food before it passes into the alimentary canal. Here in this filtering apparatus of the Appendicularian are numerous naked Rhizopods and Gymnodineae, together with smaller skeleton-carrying Rhizopoda, completely absent from the net catches. It is obvious, therefore, that if a complete knowledge of the plankton is to be gained, other methods must be applied. It was assumed that the loss of plankton by the use of No. 20 silk in the net was unimportant, and that the real masses of plankton in the sea might be only 2 to 3 times greater than the figures given by the net. This would certainly be of no great importance if only the volume or weight of the plankton present was required without any reference to its constitution. If one requires however, the chemical constitution, it 1s quite incorrect, and this applies further to the qualitative and quantita- tive counting method, because the animals and plants in the catch will occur in quite different relative proportions from the true conditions present in the sea. Since the mesh work of the net itself has a large area, many of the small forms which could pass easily through the meshes will be caught on the net tissue itself; and this will give a more deceptive appearance of reliability than if these forms had altogether escaped. Again, the fractions of these small forms caught is not always the same, because if the sea contains a great number of diatoms (as Chaetoceros), the meshes of the net will be gradually filled up, and the spines interlocking will cause the net to act asa much finer filtering material and hold back many species which would otherwise slip through. This accounts very often for the large catches with the nets, when diatoms are very abundant. By comparison of the net catches with the other quantitative 522 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. catches made by the apparatus to be described below, it has been found that the Metazoa, with few exceptions, are completely or sufficiently caught by the plankton net, whilst of the Protozoa only a few large forms, Voctiluca, Ceratium tripos, &e., or species with long spines, will be obtained. In fact, the number of individuals present in | the sea is from 5 to 100 times greater than is demonstrated by the net, and the species which form this loss are not of “no importance,” but are the chief forms of food for the larger species, and therefore of great significance in the metabolism or see-saw of life in the ocean. If, there- fore, the Metazoa or larger Protozoa and Protophyta only are to be studied, the net can be used as the best instru- ment by far for the capture, whether for quantitative or qualitative purposes. If a complete investigation of the plankton is to be made, and the relation of larvae to adults and food to the eaters of it are to be considered, other kinds of apparatus must be used. Of these, the most important is the Pump and Tube, by which water is pumped up to the boat and later is filtered. In shallow water, and up to 100 metres deep, the net can be more or less supplanted by the pumping method, but, unfortu- nately, for greater depths, and for regions where there are strong currents, the pumping method is hardly appleable. Pump, T'usr, AnD FitrerR MrtTHoD. Essentially the method consists in the pumping up of a vertical column of water, which is filtered on the vessel or, later, on shore. An indiarubber tube of sufficient length for the deepest regions is required, and this is lowered vertically in the water by means of a rope attached to the lower end, and in the same way is slowly pulled up, whilst at the same time the water is pumped out of the upper end by a small brass pump. METHODS OF PLANKTON RESEARCH. 523 By lowermg the tube it fills gradually with water out of the various depths through which the lower end sinks, so that finally it contains a water column, consisting of water from all depths between the surface and the lowest peint reached. When the tube is again slowly raised through this column to the surface, it 1s once more filled by water from each layer. Thus by repeatedly lowering and raising, whilst the pump is worked, any quantity of water may be obtained, representing a vertical column whose height is that from the lowest point reached by the tube up to the surface and whose other dimensions can be reckoned directly from the volume of water collected. 3 The water in the sea will naturally rise in the pump tube of its own accord until it attains the same level as the surface. It is only necessary, therefore, to use the pump to lift the water from the surface of the sea into the boat, and a small pump is accordingly quite sufficient. It is even possible in a boat with a deep bottom, where the upper end of the tube can be placed lower than the surface of the sea, to siphon up the water, but usually, owing to the motion of the boat, this method is not successful. The whole length of the tube should be fastened to a rope which will bear its weight. If currents are present, the rope and pipe must be kept vertical by means of a sinker. A very simple and cheap arrangement was con- structed and used by Lohmann in the Mediterranean (13), so that the simple turning of a windlass both worked the pump and pulled up the tube. ‘Thus the rate of pumping and the pulling up of the tube were always in the same relation, however quickly the windlass was turned. Moreover, the direction in which the windlass was turned had no effect on the working of the pump, 524 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. which continued to raise water whilst the tube was either lowered or raised. Since it is questionable whether this method of sucking up the water would have an effect on the catch, the entrance of the plankton and its passage up a tube was observed by Lohmann by using a glass tube. It was distinctly seen that the organisms in the centre of the tube ascended more rapidly than those against the walls. This difference in the current is, however, of no wmportance for the equal raising of the whole water column, because from each section the same quantity of central and peripheral water will be taken up respectively. It was noticed that some of the large animals were sensitive to the streaming, and Copepods, for example, moved energetically against the current. If, therefore, the current is slow, it is possible for the larger forms to move out of the tube, but, since the average speed of the current is 57 cm. per second, this is impossible; and any loss occurring when the pumping method ts used applies only to the destruction of fragile forms in the filtration. The water must be filtered, either on the ship or when conveyed back to the laboratory. The latter is probably the more simple. The water is pumped into large sulphuric acid “carboys” of about 28 litres con- tents, and a 4 htre of commercial formol is added so that a 2 per cent. solution results, which suffices to kill the organisms and to fix them. The filter is simply hardened paper, which is folded into a cone and is held in a zinc funnel of about 50 centimetres diameter at the mouth. It is best to construct an arrangement so that the water can run from the carboys into the filter at the same speed as the latter filters. The whole can be then left to run of its own accord, with but an occasional glance to see that the filter does not become stopped. METHODS OF PLANKTON RESEARCH. 525 The filter is carefully washed down towards the point of the cone when all the water has been filtered, and this is perforated by a pointed glass rod, whilst held over a bottle for the reception of the catch. The filtrate is then carefully washed through the perforation by means of a wash bottle provided with a strong indiarubber ball, in order to get a powerful current. The original volume of water collected being known, the catch as now obtained can be diluted and portions extracted for counting as explained above. By fishing with the net and also with the pump and tube simultaneously, or directly after one another, and comparing the results, it is possible to determine the loss by the net due to its inability to retain the smaller forms. If, however, exactly hke methods are employed at the same time and place, and close to one another, the catch is different. This divergence, due to an irregularity in the distribution of the organisms in the sea, has been emphasised by Herdman and will be mentioned later. It must be borne in mind, therefore, when comparing the unlike methods, that a certain irregularity in distribution already exists. After reckoning the volume of water filtered by the net and reducing the number of organisms found in the whole catch to the number present in a volume of water equal to that collected by the pump, it was found by Lohmann that in the case of Copepod nauplii the net lost 745 per cent. This is a very important constituent of the plankton fauna. Other organisms were present in 1,000 litres of water in the following numbers :— Silk net Pump, tube No. 20 and filter. GIODIGE INIA: Secisstnns ons Moat oon: 250 2,125 PRACIONAGIANS 25.2 cose ats ce jcssiese ons 2,350 3,860 Cystotiagellates. isha Seer. cee 20 20 PEM phebihiGAG, «2 2.ecst eae iceoana A475 19,900 Waked e1ltates ‘J... 2tiestssceedes some 35,300 526 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. — The Radiolarians were caught almost equally well by the net owing to their shape and large spines. The Tintinnidae could’ easily slip through when meeting the net in the direction of their long axis. For Diatoms and Peridiniae, &e., the following results were obtained :— Silk net Pump, tube No. 20 and filter. Sceletomendlans ists cccrskie selene aes 418 Cosciniodiscidaiem ia..cseesaeeee ae 141 6,444 Rhizosolenia alata ........2...... 1,143 4,013 Chaetoceros Ehrenbergi......... 44,317 149,793 Ceratimal GrIpOS! <......:es4sese—ne about equal in each. Peridinium divergens............ 72 317 bi NO) OWES Sosaaenee sce 15 1,190 5 MeL CIGUTI Apert 5 1,089 Coccolatihidael yen asses eee 28 11,267 Dictyochay cacess.. spose aee 54 6,241 The comparisons for the Protophyta show, therefore, that the constitution of the plankton catch was completely altered by the use of the pump and filter. Out of more than 2,000,000 plants only 110,000 were caught by the net with No. 20 silk, and 9,000 animals out of the one- third million caught by the pump and filter. The actual numbers have, however, not so much value, because the smallest organisms give the largest numbers for the loss. If the mass, however, be calculated it is found that the pump and filter gave 52°4 c.cm. as total catch out of 1,000 litres, whilst only 21 c.cm. were caught by the net. Hence the constitution of the plankton, formerly determined solely by net catches, must contain greater errors for many forms than were supposed. Meruop oF INVESTIGATION FOR THE SMALLEST ORGANISMS. It has been demonstrated by several observers that many of the small and fragile forms, without skeleton, are either destroyed completely during the filtration or METHODS OF PLANKTON RESEARCH. DF pass through the filter, so that even the method with pump and filter fails to give the smallest forms and also the bacteria. This loss is easily seen by an investigation of the filtrates from a hardened paper filter, which reveals the fact that as much as 26 per cent. of the Gymnodineae and the same per cent. of naked Chrysomonads can pass through; and a much greater percentage of bacteria would be found to have done so. Of even greater importance than this loss is the fact that many softened fragile forms are killed by the filtration, and Monads, Amoebidae, and small Gymnodinae will be absent for that reason from the filter catches. More- over, it is very difficult to recognise most of these forms when fixed and preserved, and, therefore, for these forms alone it is necessary to use other apparatus which does not require any filtering mechanism and which will allow of the organisms being studied in the living condition. The apparatus consists of (1) a means for procuring samples of water from different depths, and (2) a centri- fuge. By this method small water samples can be taken and examined from the various parts of a water column down to the greatest depths in the ocean, and from these, by interpolation, the average number or volume of organisms present in the complete vertical column can be calculated. A “Kriimmel” water bottle (fig. 4) is the most satisfactory for the purpose of obtaining water samples. It is already made sufficiently large to bring up three litres of water from any depth required, which is sufficient to allow of a portion being used for the determination of the hydrographical conditions—an absolute necessity in plankton work. The water bottle is lowered open and closed at the required depth by a falling weight, sent 528 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. down the rope from the surface. The water required for the centrifugal investigation is taken from the water bottle, received in glass-stoppered bottles and placed in a cool and suitable place until the laboratory is reached: the examination should take place as soon as_ possible after the catch 1s made. The employment of the centrifuge for this work was first suggested by Cori (6). but it has not been much used, as it was pointed out that the action on various organisms is selec- tive, and the sediment is therefore not in its constitution a true sample of the plankton present. This selection does not come into play if the organisms are dead and in a preserving fluid that is hghter than water, consequently Kofoid has used the method for catches preserved in alcohol. Dolley (16), by using a very powerful centrifuge which he termed the “ Plankton-okrit,” and which gave 8,000 revolutions per minute, had complete success in the sedimenta- tion of living plankton. Other American workers, also, have used this method, and have found that for accuracy of determination it ae, poe ee water toy exceeds all other methods at present employed. Kofoid, however, raised the objection due to its selective influence, and found that many organisms would not form a sediment. One must remember that no method will be accurate for all forms, and none of the METHODS OF PLANKTON RESEARCH. 529 methods here described will alone give an accurate sample of all the forms present in the plankton. Lohmann has used with success a centrifuge which carries four glass tubes and which gave easily 1,3U0 revolutions per minute when turned by hand. He found that 9,000 revolutions, in seven minutes, were usually sufficient. - For the investigation of the hving forms, samples of only 5 to 15c.cm. are taken. ‘The tubes for containing the sample, on the centrifuge, are small cylindrical vessels, with the point drawn out slightly to form a cone- shaped end, in which the material will form a well- defined sediment. After the completion of centrifugation, most of the water can be poured away, and the sediment remains undisturbed with the water that fills the conical end. By means of a pipette, the sediment, through repeated sucking up and forcing out, is finely distributed in the water remaining, and is finally completely sucked up and transferred to the glass numbering plate used with a specially constructed microscope stage. This is much smaller than the numbering stage for the large net catches, is comparatively cheap, and can be fitted to any microscope.” The conical end of the tube is now washed out with a very little water (some of that originally poured off), and this is added to the main part of the catch on the glass plate. The whole catch should form only a single drop, such as can be covered with an ordinary 12 mm. cover glass. If the water contains many flagellates and ciliates, the counting of such rapidly moving organisms is impossible. The cover glass should then be held over * Zwickert, Optician, Kiel, is the maker of this stage. 5380 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. osmium vapour for a short time before being placed on the drop of water and sediment, which is sufficient to cause narcotisation. When high powers are used, it is impossible to count the organisms in the complete area of the drop. In this case only a fraction is counted, in the following way. The glass counting plate on which the drop rests is crossed by a series of parallel lines running in one direction, from the observer. If the number of spaces between the lines, which are covered by the whole deposit when the cover glass has been applied, is divided by five, that gives the spaces in which the organisms should be counted in order to arrive at one-fifth of the total in the catch. These spaces counted should be equally distributed over the whole area, so that an average can be obtained. It is best first to count the organisms in one-fifth of the mass with a high power for the smallest and most frequent forms, and then, under lower magnification, the whole mass for the larger and less frequent. It is well also to take another quarter of a htre of the same sample from the Kriimmel bottle (fig. 4) and add formaline to make a 1 to 2 per cent. solution. After this liquid is partly removed from the catch by filtration through very fine filter paper, the residue can be centrifuged and compared with the centrifuged samples of ving forms. The amount of water taken for the centrifugation of the latter must depend on the number . of organisms present. If 15 c.cm. of water are first taken and centrifuged, and too many organisms are found for an easy count, then it should be discarded and a smaller quantity taken. The extremely small quantity of water taken for these samples is astounding and might be considered in- sufficient for two reasons: —First, that not enough animal METHODS OF PLANKTON RESEARCH. 531 and plant life are present in such small volumes; and, secondly, that they are absurdly small for quantitative estimations of a column of water or for finding the true conditions in the area where the samples are taken. This does not, however, seem to be the case; and with regard to the first point, it is surprising what a mass of material 15 c.cm. of water gives with the centrifuge, so much that Lohmann had often to take less. The second difficulty is also only apparent, because when the Hensen plankton nets are used the sample of water taken for counting bears an equally extremely small relation to the quantity of water that has passed through the net. The only real difference between the two former methods, the net and pump and filter, and this method is, that in the former the plankton is collected from relatively large masses of water, and small quantities are taken out of this as samples for counting, whilst by the centrifugal method the small quantities are taken directly from the sea. In stating this, however, we are again confronted by the doubt as to the equal distribution of the plankton in the. sea, which will be mentioned later. Lohmann thinks that the distribution is sufficiently hke to allow of such small samples being reliable guides to the quantitative constitution of the plankton. In order finally to calculate the average number of organisms present in a column of water, from which various samples have been taken at various depths, the following formula should be used. Assuming that the samples A, B, C, D are taken at increasing depths, separated by the distances a, b, c, then A is the average for the column. Aa+ B(a+6)+ C(b+c)+ De 2(a+6+¢c) If one wishes to make a complete investigation of LL 582. TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. the plankton, either qualitatively or quantitatively, one must use all the three above methods side by side. If only a definite part of the plankton is to be studied, then the method must be chosen to suit the case. For large crustacea, fish eggs, and medusae and other large plankton forms occurring but seldom in the water, in comparison to the Copepoda and smaller forms generally, the large Hensen net described by Jenkins should be used, to work through much larger quantities of water. For the main constituents of the plankton, the Copepods, Ceratium, and, in fact, for general use, the Middle Plankton Net of Apstein is to be preferred. This has been the chief instrument used in German investigations, and holds its place because of the ease of working and the general applicability. It must be borne in mind, however, that when these nets are used there is a con- siderable loss, as has been shown above, and, therefore, when possible, the use of the net should be replaced by the pump, tube and filter. In fact, in water of moderate depths, and shallow water, the pump method is “the” method for plankton investigation, and the net and centrifuge should be used only to complete the results when the greatest possible accuracy is required and the complete constitution of the plankton is to be discovered. The points against the pump method are the difficulties encountered in deep water or when there is a strong current, together with the greater time that is required ~ for pumping and filtering. There is another possible method for arriving at these results, which could be applied to the greatest depths, and in comparatively stormy weather. It is to use a water bottle for collecting a volume sufficiently large to allow of its being filtered and examined in the same way as the water from the pump. In this way, METHODS OF PLANKTON RESEARCH. 533 however, the contents of a vertical water column would have to be calculated from the samples taken at various depths. For this purpose, too, it would be necessary to obtain more water than is brought up by the bottles now in use. The Kriimmel bottle as now used by hydro- graphers has three litre contents, and there should be no difficulty in increasing the size to five litres, which would give a sufficiently large sample. OTHER PLANKTON APPARATUS USED FOR QUALITATIVE WorK. The apparatus above described is intended for the quantitative estimation of the plankton in volume, chemical constitution, or by the counting method of Hensen. For mere purposes of qualitative investigation the procedure is naturally much more simple. The net described is, in any case, of great use as a vertical net, and would completely supplant the pump and filter, whilst the centrifuge would be used to catch organisms that pass through the net. Under special circumstances, however, other nets are used, which are coarser, and have their special use according as they are for surface or deep work, and for small, large, or very large organisms. Again, it is sometimes desirable to investi- gate the plankton of areas over which the ship is passing at a considerable speed, and for this purpose other devices are necessary. For general use in qualitative work there is the ordinary small tow-net, well known at all biological stations. This is constructed out of bolting silk, and has the same conical shape as the vertical net, but does not have a mouth-piece as described for the quantitative nets. No calculations can be made as to the quantity of water it filters. These nets are generally used for 5384 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. horizontal fishing, and should be made with No. 20 silk for smaller organisms, and with No. 12 or No. 3 when larger forms are specially required, since with these latter silks more water will be filtered in a shorter time, and the catch will be free from the masses of small diatoms, which are not wanted. All plankton nets should be fitted with a metal filtering bucket attached to a brass ring, which forms the base of the net, by means of a screw attachment, or by the simple device of a bayonet joint. This bucket consists simply of a brass cylinder, the size varying according to the size of the net; the lower end is closed by a piece of silk of the same mesh as that used for the net, and attached to the brass cylinder by means of a clamp ring. 7 When the net has been used, it is only necessary to wash it down with a few pails of water thrown on the outside, and to unscrew the bucket with the catch. If time is short, and the catch has to be preserved as soon as possible, the silk itself can be removed from the bottont of the bucket, rolled up, and dropped into a bottle of alcohol without removing the organisms; a new piece of silk is then placed on the bucket and it is ready for further use. For fishing pelagic eggs, young larval stages of fishes, or when large catches are desired for histological or anat- omical work of large plankton organisms, such as Medusae, very large Copepods, Sagittae, pelagic worms, &c., the German “Brutnetz” is a very successful instrument. This, as the name implies, was constructed for fish eggs and larvae. It is much cheaper than the silk nets, since it is constructed of “ cheese cloth,” or of good canvas. This is simply a conical net about three metres long, the mouth of which is kept open by a wooden ring of cane 80 to METHODS OF PLANKTON RESEARCH. 535 90 cm. in diameter. About one metre from the mouth the net is attached to a second wooden ring, to one point of which is attached an additional rope from the ship, so that when the haul has been made the net may be rapidly pulled up edgewise without offering opposition to the water. The apex of the net where the usual bucket is attached has a diameter of 10 centimetres. A modification of the “Brut” net, called the “ Scherbrutnetz,” has been constructed to allow of the application of such a net as the former to the collection of the plankton from deeper layers. The essential feature is a strong galvanised iron plate, hinged, as seen in fig. 5, Fig. 5.—The ‘‘ Scherbrutnetz.”’ 6 to one side of the square mouth of the net. This ‘* shear ” board is, however, not allowed to move freely, but is fixed so that it makes an angle of 125° with the plane of the mouth of the net. When this net is hauled the water presses against 586 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. the “shear” plate exactly as on the otter boards of the otter trawl, or like the wind on a “ kite,” causing, in this case, the net to sink in the water. Knowing the length of rope allowed to run out, the true depth of the net can be easily found by using the Apstein apparatus already described and measuring the angle the rope makes with the horizon. A still larger net than the “ Brut” net is sometimes desirable where very large catches are required of the larger plankton forms from deep water. For this purpose there is the so-called “ Kniippel” net (fig. 6), which is is titicknanerocoree tina POE rand BOOS BS ha 4 # oA Fig. 6.—The ‘ Kniuppel”’ net. worked on the principle of the otter trawl. The Kniippel net can only be worked satisfactorily when a fair sized vessel is available with a steam winch. The net which I have seen in use has the following dimensions. The net itself is made of strong canvas and is about 15 to 20 feet long, the mouth is square, each side of the square having a length of 8 feet, and each of the mouth edges is formed by a broad piece of sailcloth, to which the filtering canvas is sewn. The apex of the net is as usual fixed to a metal bucket, in this case about 9 inches in diameter. The two vertical sides of the mouth of the net are fixed at intervals to two stout poles (fig. 6, 6. and c¢.) 9 feet long, and provided at the lower end with a heavy lead sinker METHODS OF PLANKTON RESEARCH, 5387 (fig. 6, f. 7.) in order to keep them vertical in the water. Kach pole is attached by two strong ropes, fixed to the upper and lower ends respectively, to the “ otter” boards (fig. 6, d.e.). The ropes are about 12 feet long, and represent the “foot rope” and “head line” of the otter trawl. The otter boards are strong wooden structures bound with iron, and measure 4 feet by 2 feet. When the net is lowered it sinks, owing to its weight, and the pressure of the water forces the two otter boards out- _ wards, thus pulling the two vertical poles as far apart as possible, and in this way the mouth of the net is kept open. ‘This net can be used satisfactorily at very con- siderable depths. There remains to be described a very convenient and simple little instrument by which catches can be made whilst a vessel is travelling at a considerable speed, and, consequently, any changes in the nature of the plankton between two stations can be followed without interfering with the progress of the steamer. Several instruments have been invented for this purpose, but it will only be > which necessary to mention here the “ Plankton Rolire,’ was invented by Apstein and has not yet been described. It has the great advantage of being simple, and so small that it can be very easily carried about with one, so that plankton catches may be made on a sea voyage other than a scientific expedition. Fig. 7 shows the external appearance of the instrument. The Plankton Rohre consists simply of a brass tube 25 cm. long, one end of which, however, is not of the same diameter as the rest of the tube, but forms a truncated cone, making the mouth opening of the tube very narrow. The diameter of the cylindrical section of the tube is 3°5 cm., and the length 22°5 cm. The conical mouth-part is 2°6 cm. in length, and the opening is only 1 cm. in diameter. This narrow opening 538 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. is for the entrance of the water, and is, therefore, the front end. The other end of the tube is closed by the filtering apparatus—simply a piece of No. 20 bolting silk, or coarser, if required, which is fixed in the usual manner by a clamp ring. To one side of the tube is attached a heavy strip of lead (fig. 7) to keep the instrument from being pulled out of the water. This will consequently be the under side, and to the opposite and upper sides of the tube, at the front end of the cylindrical portion, two ring attach- | ments are screwed, by which the whole apparatus is = Fig. 7.—The ‘‘ Plankton-Rohre.’’ fastened to the hauling rope. The action of the instru- ment, when pulled at a considerable speed, depends on the small area of the opening, which allows but little water to enter, and therefore there is but little strain on the silk tissue, so that this 1s not torn nor are the organisms damaged. I have seen it used successfully at a speed of eight and a half knots. One disadvantage is that very small catches are obtained, even when towed rapidly for a quarter or half an hour, but since the apparatus was not intended for obtaining large quantities, this does not detract from its usefulness. METHODS OF PLANKTON RESEARCH. 539 RESULTS OF THE PLANKTON WorkK AND Its AIMS. I propose now to discuss briefly some of the results obtained by the quantitative method, and the present position of the work. The first ideas came from Hensen’s investigation into the distribution of the eggs of the plaice in Kiel Bay. These are planktonic eggs, which float as long as the salt contents of the water does not sink below 178 per cent., and this is seldom the case in the West Baltic. It became evident that these eggs extruded at many spawning grounds, must necessarily distribute themselves widely, and the longer they remain floating the more movement will take place and the more equal the distribution will become. On this equal distribution of the plankton particular stress must be laid, because it forms the foundation on which the value of the quanti- tative work depends. ‘The investigation of these fish eggs led to notice being taken of the other planktonic organisms, and, finally, Hensen says—‘ The sea has its yearly production in animals and plants, just in the same way as a garden or field. For the land, it is an almost impossible problem to work out this production, because even if one, with extreme weariness, worked out the fauna and flora completely and quantitatively for a small area, at a short distance from this point the conditions and distribution would be altogether different, and we could never be certain that what was found in the small area would be a true sample for a large area. In the sea the conditions are quite different, the species and number remain to a certain extent everywhere constant.” Thus, with two fundamental hypotheses the quanti- tative method has been applied. These are, first, that the plankton organisms are equally distributed in the sea where like conditions of existence are found; and, second, 540 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. that this equal distribution is sufficiently exact to allow of relatively small quantities of water being taken as samples of the total production of the area. Amongst appheations of the plankton quantitative method, the following are perhaps the chief :— 1. To estimate the produce of the sea or ocean or any particular area per year, and to compare the produc- tiveness of different regions. | 2. To investigate the dependence of the plankton as a whole, and also of the different organisms, on the hydrographical conditions, such as lhght intensity, temperature of the water, salt contents, currents, and, at the surface, wind and waves. 3. To investigate the relations existing between the different plankton organisms themselves, their dependence ce on one another, and the relation between the “ eaters ”’ and the “ eaten.” | 4. To investigate the reproduction of the various plankton organisms, and of others not planktonic, but whose eggs or larvae are pelagic; the relations existing between the number of eggs, the number of larvae and the adults, and the length of time occupied in the life history. | For the purpose of investigating the condition of the plankton on the high seas, the “ Humboldt-Stiftung Expedition” already alluded to was fitted out, no doubt | stimulated by the results of the English “ Challenger ” Expedition. Not all the German zoologists were in favour of the object, and Haeckel in particular wrote against it (2), arguing that the pelagic organisms were not equally distributed, but that they travelled in swarms, or at least were so irregular in their occurrence that samples taken at.some distance from each other would be valueless for a quantitative estimation. He has been answered in detail 4 : METHODS OF PLANKTON RESEARCH. 541 by Hensen (3). The vessel chosen for the voyage, the “ National,” started from Kiel, July 6th, 1889, and pro- ceeded northwards through the Kattegat and Skagerack, and then across the Atlantic Ocean to Greenland. Vertical plankton hauls were taken at intervals on the way. From Greenland the course was directed 8.W. for the Bermudas, and consequently went over the banks of Newfoundland and across both the Arctic Labrador Current and the warm waters of the Gulf Stream. From the Bermudas the course ran almost parallel to 30° N. lat., and thence across the Sargasso Sea, until the meridian of 38° W. was crossed, and the Cape Verde Isles steered for. This direction was followed further to the S.E. up to the Island of Ascension, then west again over the ocean to the Amazon’s mouth, practically along the South Equatorial Current. From the latter place the vessel returned direct to the English Channel. The series of reports by specialists on the different groups of pelagic organisms are not yet all published, and the general conclusions have not yet been put together, but from some results given by Hensen (4), it was shown that the quantitative catches agreed, as far as volume is concerned, far better than was expected, and gave still further proof of the equal distribution of the plankton. Several interesting points were brought to light in connec- tion with the distribution. An unexpected result was that, contrary to the conditions existing on the land for both animal and plant life, the plankton was decidedly more abundant in cold and temperate regions than in the tropics. The difference in volume in the catches between Greenland and the Hebrides and those taken from the Sargasso Sea is truly remarkable. This result was quite unexpected by those who had worked at the material rich in species, taken by the ~ 542 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. y “Challenger ”’ in the warmer seas, but since these were only qualitative catches, no comparison could be made, and we are faced with another problem—What condition is it in the sea which makes it more favourable for life in the colder regions? This has been referred to in an important paper by Brandt (9), which should lead to further investigation. The catches, however, made in the cooler regions are in reality much smaller than they appear, because the bulk of the organisms present are diatoms. When the volume of plankton is estimated by allowing the catch to settle down for 24 to 48 hours, an easy, but not always reliable method, it will be seen that a diatom catch refuses to sedimate as one where Copepoda or Ceratium are present. Thus a diatom catch appears to have a much greater volume than is really the case, even after it has stood for weeks. Furthermore, as Lohmann has since pointed out, the presence of diatoms in considerable quantity increases enormously the catch because the diatoms entangle themselves over the meshes of the net, and render it a much finer filtering tissue. In the tables given in the published results of the expedition there 1s in one case an increase in the catch between the stations of from 5 c.cm. to 156. This sudden increase was due to Calanus finmarchicus; and one must evidently consider this as a swarm. ‘The nearest land was 500 miles distant, and, after the large catch, the catches at the following stations again showed quite a small volume. It is a well-known fact that the Siphonophora, Porpita and Velella, are found travelling in great shoals together, and in the accounts of the expedition we find that south of the Cape Verde Isles shoals were very frequently met with, amongst which occurred swarms of METHODS OF PLANKTON RESEARCH. 543 Physaha, Pyrosoma, Salpa, Schizopods, Janthina, Beroe, Pteropods. Thus, one of the nets with an opening of 1:13 square metres hauled up from a depth of 500 metres 520 Pyrosoma on one occasion. The question is—-What has brought these together? Neither wind nor their own motion, unless governed in some way unknown to us, could do this. At another place 5,860 Doliolum were caught in one haul of the net, as against 1,500 in all the other catches together. Darwin, and other observers, had previously recorded the fact that long stretches of the sea were frequently met with, deeply coloured by the abundance of some animal or plant species, as, for example, T'richodesmiwm erythraeum. It is this association of planktonic organisms in swarms that is now being investigated by Herdman (17), and it will be interesting to see how far it extends. (See also 19.) With the exceptions of some swarms, Hensen main- tains that the equal distribution was never disturbed to such an extent, where the conditions remained the same, as to render the application of the quantitative method unsatisfactory. In the Sargasso Sea, for example, where there is no current practically speaking, the catches were astonishingly small, but the volume remained constant over a stretch of some thousand miles. It is possible, however, that the constitution of the catch was altered. The results of this expedition tend to show that the ocean waters are very poor in plankton. There is a sharp distinction existing between oceanic and coastal forms; many of the oceanic species are never or only exception- ally seen near the coast, and one must visit an oceanic island in order to study them. What is the barrier to this distribution? The oceanic species are neither more frail nor more nor less active than many of the coastal 544 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. forms. This brings up the whole subject of the different conditions to which the planktonic flora and fauna are subjected in oceanic and coastal regions. It is an important point, because though the oceanic regions are of very great extent, the waters that are of practical importance for fisheries are our coastal seas, like the North Sea, the Irish Sea, &c., where the depth is nowhere very great, but where the plankton is very abundant, and where a thorough planktonic investigation should be of considerable economic value. The bottom - of these seas and all coasts is inhabited by a large and varied animal and vegetable population; the laminarian zone, for example, is probably the richest area of the earth’s surface in animal life. From the Echinoderms, the Crustacea, the fish, &c., found in these shallow seas arise myriads of larval forms, which, after a pelagic life, again migrate to the bottom and continue their existence as fixed or sedentary animals. Thus the plankton of the Irish Sea is made up to a very large extent of eggs and larvae of animals which are not pelagic when adult. In one group the Crustacea, for example, there are orders like the Copepoda, which are typical plankton forms and remain, with few exceptions, free-swimming and pelagic during their whole life; while the Cirripedia, on the contrary, have the pelagic larval forms, but their adults are fixed, and therefore not constituents of the plankton. Then, again, the Hydrozoa contain forms which alternate between a fixed hydroid generation and the free medusoid of the plankton. Certain Nereis species are to be found creeping about the bottom or swimming sluggishly, but when sexually mature undergo a considerable change in structure, the parapodia become modified for swimming, and the so-called Heteronereis stage may then be caught in considerable numbers in: the plankton nets on METHODS OF PLANKTON RESEARCH. 545 the surface itself. Thus the coastal plankton is made up of very diverse forms, partly always plankton, partly plankton during only certain periods in the life history. Out on the high seas, where the ocean floor is a waste as far as fixed living plants are concerned, and the water is 2,000 or more fathoms deep, the plankton contains no forms arising from the bottom. Thus the oceanic plankton is subjected to different conditions of existence, and the absence of these forms in general from our coasts is probably due to their failure to compete with the abundant pelagic life of the shallower waters. The ocean, according to the figures provided by the oceanic quantita- tive plankton expeditions, may be considered as a desert, receiving its life from all sides, and from this producing forms that are peculiar to it, and have in the struggle for existence been driven further out. It is now obvious that the most important regions for the employment of quantitative methods are areas hke the North Sea and the Imsh Sea, or coastal water generally, where, since the plankton is of great import- ance as the food of fishes and contains the eggs and larvae of the latter, the results may be apphed to the elucidation of problems in fishery work. It 1s necessary, also, to determine to what extent the plankton is dependent upon the various hydrographical conditions, and also what variations occur during the year. Since the year 1901, Great Britain, Germany, Norway, Sweden, and other countries in Europe bounding the North Sea and Baltic, have together investigated the hydrographical and biological conditions of these two areas. Grants have been given by the Governments concerned and suitable steamers provided, and an International Committee has drawn up a programme in accordance with which various stations are visited four times a year, and scientific 546 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. observations are carried out simultaneously, with the object of making a complete investigation of the whole area. One of the most important questions is, naturally, the condition of the plankton at different places in these areas at the same time, and the variations during the year. Since at the time that these plankton investigations are carried out, the hydrographical conditions are also very thoroughly observed, there is an excellent oppor- tunity of comparing both. Unfortunately, so far as the plankton research is concerned, the only result of these voyages four times a year has been the publishing of a great series of tables, which, for purposes of comparison, are practically worthless, since only one country, Germany, has used the counting method of Hensen. The total failure of the ordinary methods of estimation has already been discussed above, and it was then pointed out that, if the problems are to be solved, the more scientific method of counting the organisms must be adopted. The distribution of plankton and its relation to the hydrographical conditions has, to a certain extent, been worked out by Apstein and others for the Baltic and North Sea, from the catches made on the quarterly expeditions, for the stations belonging to the German section (15). It has been found of very great importance to use the closing net, and, in addition to a vertical haul from the bottom to the surface, to divide this column up into sections, as, for example, where the depth is 210 metres, a haul is : taken from 210 to 65 metres, another from 65 to 25 metres, from 25 to 5, and, lastly, from 5 metres deep to the surface. This last catch is particularly important and very often differs markedly in its constitution and volume from the others. In all probability the surface layer of water to a depth of only one metre is the layer concerned, METHODS OF PLANKION RESEARCH. 547 but, owing to wave motion, it is better to make the haul from a depth of five metres. This shallow surface layer of the sea appears to be particularly rich in plankton, and it is therefore conceivable from this how two tow-nets pulled along the surface may differ in contents if one of them is accidentally a littie heavier than _the other, or, for some reason, has been towed a little deeper. The following figures from the German North Sea catches will illustrate the differences in the volume from different depths at the same stations : — Depth at which c.cm. underlsq. c.cm.in1 cub. a was made. metre area. metre. ae metres ie te? vet ouh ie - a 56 aa 1101933 “3 af da ed, ee 1°8 ms ee 1 sae 14°4 (oa + ee 56 383 B15) =, > are 144 test 3°4 144 Te 28°8 In the Baltic, voiume estimations have been made and the catch also quantitatively examined. On one expedition, for example, the volumes from Stations 1, 2 and 3 in the West Baltic, where the salt contents was 17 to 20 °/o, were very large and above the average. At Station 8, a point further east, there was also a large catch, but the salt contents was only 8 to 10 Joo The constitution of the catch varies in the Baltic, probably with the salt contents, which, unlike the North Sea, varies within wide limits. Thus, Aphanizomenon flos-aquae increases as one travels east. Chaetoceros decipiens and C. didymum decrease and eventually drop out altogether. Ceratium also decreases in the same way. At Station 8, however, where there was a low salt contents, this decrease for some reason was not present. In the North Sea the simple hydrographical conditions of the Baltic do not prevail, and the whole matter is rendered far more MM 548 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. difficult. The total volumes and the constitution of the catches made varies considerably at the different stations, — Thus, in one of the expeditions at Station 9, North Sea, there was a greater quantity of Ceratiwm macroceros and an abnormal number of Ozthona and Pseudocalanus. At Station 11 a great number of Actinotrocha larvae formed an important constituent in the catch. In May, 1903, there was in the North Sea a remarkable preponderance of plankton in the upper five-metre layer, far exceeding that of the deeper layers. This was quite independent of the salt contents, for it occurred where there was no difference in the constitution of the sea water between the surface and the bottom. ‘Thus, at one Station the numbers for plant cells were in the pro- portion 0 to 5 metres deep, 400; 5 to 40 metres deep, 55; 40 to 75 metres deep, 8; 75 to 150 metres deep, 2; 150 to 450 metres deep, 1. In another example, however, there was a decrease as above from the surface down until the 20-metre depth was reached, but between 25 metres and 75 metres deep the average number of organisms present was twice as great as at the surface, that is, about twenty times what it should have been. This was due to an abundance of Phaeocystis. What determines these varia- | tions? Salt contents seem to have nothing to do with the diminution which occurs as one passes from the surface into deep water, though in the Baltic, as will be mentioned below, the salt contents seem to cause an opposite result. Light intensity might be connected with it, but very good catches are often obtained at depths of 75 to 100 metres. In the Baltic, in February, 1903, the figures gave different results for the vertical distribution, for the plankton was always more abundant in the deeper layers than at the surface. The organisms which caused this increase were METHODS OF PLANKTON RESEARCH. 549 Ceratium balticum, C. longrpes, C. macroceros, C. fusus, Polychaete larvae, Copepod larvae, Ozthona similis, Centropages hamatus, Paracalanus and Pseudocalanus. These are all forms which are characteristic of the North Sea and West Baltic water, where the salt contents are high. Owing to the peculiar conditions prevailing in the Baltic, a great variation occurs in the salt contents of the water, varying from 20 °/5. in the West to fresh water in the North-east, and, moreover, at any station there is commonly a great difference between the salt contents at the surface and at the bottom. It is, therefore, natural to presume here that the greater abundance of the plankton in the deeper layers was due to the salt contents of the water, since that was greater in these layers than at the surface, and the organisms present were those characteristic of salt water. At the present time, how- ever, a great deal still requires to be learnt with regard to the relations between the plankton and the hydro- graphical conditions, and in many cases the results obtained so far contradict each other. Finally, it is necessary to examine some of the extremely interesting statistics given by the Hensen method quoted by Jenkins and others. I refer first to such estimations as the number of Copepods in the West Baltic or the number of Peridinians annually devoured by a Copepod. We have only to consider how little we know of the conditions under which these plankton forms live, and the admitted inaccuracies of the method, to see that such results must be so hypothetical as to be of very little practical importance. To one of the calculations I must refer in greater detail. The number of floating eggs of the cod and flat fishes found in the Kckenférde waters, the area of which is 16 miles, was estimated at 30 per square metre of the 550 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. surface for January, 45 to 50 for February, 60 for March, . and 50 for April. The average depth of water is given as 20 metres, and the eggs take 15 days on the average, under the conditions prevailing in the Baltic, to develop, so that the above numbers must be doubled to give the number of eggs present per month under a square metre of surface water. This gives 370 eggs per square metre for the period January to April. From the returns of the Hekenfoérde fishermen, it was calculated that the cod and plaice annually caught would have produced 25,400 million cod and 73,895 million plaice eggs annually, if left in the sea. These figures gave for every square metre of the 16 square miles over 26°6 cod and 84 plaice eggs, a total of 110°6 eggs, which represented the loss through the fish being caught. If this is added to the number 370 above calculated, the total 480°6 is the number of eggs produced by all the cod and plaice, captured and free, yearly for every square metre of surface water. The relation 110°6: 480°6=1: 44, and this is described as giving the ratio of the adult fish caught annually to the total number present in this area—a capture of a quarter of the total fish. | This argument is, however, incorrect for the follow- ing reasons. ‘I'he number 110°6 represents the number of eggs under each square metre of the surface, assuming that all the eggs had survived which the fish caught annually were capable of producing in their ovaries. The numbers 23,400 million cod eggs and 73,895 million plaice eggs were arrived at from direct estimations of the number of eggs in the mature fishes. Now, it is well known that the cod and plaice produce a very large number of eggs, but that out of the enormous number only a certain proportion survive. Hence the need for such a MELrHODS OF PLANKTON RESEARCH. 551 large number, and hence, also, the attempts made by fish hatcheries to save a greater number of the embryos by rearing them through the early stages. Then, again, since unfertilised plaice and cod eggs do not remain pelagic and other dead eggs fall to the bettom (when their death is not due to their being devoured), the floating eggs capable of being caught must be but a small proportion of the number actually produced. Hence the number 110°6 is much too high, as a calculation of the number of eggs per square metre lost by the capture of the adult fish, and cannot be compared directly with the number 370, which although the actual number of eggs fished, represents only a portion of those produced. The calculation has assumed that the relation between the number of eggs floating in the sea and the fishes that produced them is the same as that between the number of eggs in the ovaries and a mature fish. In conclusion, it may be repeated that for a scientific quantitative study of the plankton, the complete apparatus and the Hensen method of counting must be employed. It is quite obvious that a certain amount of inaccuracy will occur with the use of each piece of apparatus, and the numbers must be considered approximate only; but since the errors will average the same for each catch, they do not invalidate the results for purposes of comparison. It is quite another matter, on the other hand, if the plankton is found to be not so equally distributed that the small samples taken will give reliable results for the whole areas. It is not to be expected that under varying hydrographical conditions the plankton will remain the same; but, at the present time, very little is known of the actual relations. Again, it has been pointed out several times in this paper that the results of recent plankton work have very often shown sudden and striking 552 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. variations in the quantity and constitution of the catches at two stations where apparently the conditions prevailing were the same. Hensen and the later German workers regard these fluctuations that occur as of little import- ance; but it is clear that more knowledge upon this question of the unequal distribution is required, because if small samples (and they are only 15 c.cm. for the centrifuge) are to be taken, they will give no true picture of the plankton present in either quantity or quality, nor of the relations of larvae to adults, if swarms occur or 1f there is unequal distribution to any considerable extent. It is, therefore, very necessary to take a small region and to make sure that the hydro- graphical and other conditions are the same throughout, or to take catches in exactly the same way, side by side, or separated by the length of a vessel, in order, after a systematic research, to tabulate the fluctuations that have occurred. Herdman (17), who is working on these lines at Port Erin, has already given some surprising figures of the variations in the catch of two nets worked side by side, and the detailed account of his results, to be published in this volume (see 19) should throw some hight on this very important question. METHODS OF PLANKTON RESEARCH. 558 Papers REFERRED TO ABOVE. 1. Hensen. Uber die Bestimmung des Planktons, 5 Berich der Kommission z. wissen. Unter. d. deutschen Meere, 1887. 2. HarcKket. Plankton Studien. Jena, 1896. 3. HenseN. Die Plankton Exped. u. Haeckels Darwinism1 Kiel, 1891. 4, Hensen. Ergebnisse der Plankton Exped. Band Kiel, 1892. 5. Hensen. Methodik der Untersuchungen bei der Plankto1 Exped. Ergebnisse der Plankton Exped., Band II, Kiel, 1895. 6. Cort. Uber die Verwendung der Centrifuge in der zoologische Technik. Zeitschrift. f. wissenschaft. Mikroskopie, Band XII, 1895. 7. Apstery. Das Sitisswasser plankton. Kiel, 1896. 8. Kororp. Onsome important sources of error in the Plankten method. Science, N. S., Vol. VI. 9. Branpt. Uber den Stoffwechsel im Meere. Wissensch. Meeresuntersuch., N. F., Bd. IV, Kiel, 1899. 10. Vortx. Hamburg Elbuntersuchungen. Mitt. Nat. Hist. Mus., Hamburg, Bd. XVIII. 11. Loumann. Uber das Fischen mit Netzen aus Muiergaze No. 20. Wiussensch. Meeresuntersuchungen, N. Ff. Ab., Kiel, Bd. V., Heft 2. 12. JENKINS. Methods and Results of the German Plankton Investigations. Trans. Liv. Biol. Soc., Vol. XV, 1901. 13. Lonmann. Untersuchungen tiber den Reichtum des Meeres an Plankton. Wissen. Meeresunter., N. F’. Ab., Kiel, Bd. VII. 14. ApstEern. Die Schaitzungsmethode in der Planktonforschung. Wissen. Meeresuntersuch., N. F'. Ab., Kiel, Bd. VIII. 15. ApsTEIN. Plankton in Nord-und Ost See auf den deutschen Terminfahrten. Wissen. Meeresunt., Kiel, Bd. IX. 16. Dotztry. The Planktonokrit. Proceed. Acad. Natur. Sci, Philadelphia, 1896. 17. HerrpMAn. Report of the Marine Biol. Stat. at Port Erin. Trans. Iiv. Biol. Soc., Vol. X XII, 1907. 18. Lonmann. Untersuchungen zur Festellung des vollstandigen Gehaltes des Meeres an Plankton. Kiel, 1908. 19. HerrpMAN and Scott. Intensive Study of Marine Plankton, etc., in Lancashire Sea-Fisheries Laboratory Report for 1907, p. 94. Trans. Liv. Biol. Soc., Vol. X XII, 1908. C, TINLING AND CO., LIMITED, PRINTERS, VICTORIA STREET, LIVERPOOL. ‘el “ie mayaka x \ tre Sua . Se eprre. (aaa pd \ fis M‘Farlane &Erskine, Lith.Edin® Fig. 63. y P. del. Memoir XVI. % PLATE XL “dsc RaTCUEE asl DOUGH wale ; aula lara 2 eae LH ETT rt SCONE me Ra nek Ega0D Ne pr nts / inne fo} CROBOREE Osx ia4: ~ mae - ANG =, hy a te er vba p asi MATER tes ie ey | Zee “Mig Lt i sbé.trr------- Siasea + rele we re mah r “~ all? al yi ly +8 ”* ‘ ahi) hs ANY > if RENT TT SSeS SAY pa i ) a mers at SENS! — a i a MFarlane &Erskine, Lith, Edint Prate Alp L.M.B. C.Memorr XVI. =) 0 S 0 99° dint MiFarlane &Ershine,Li L.M_B.C. Memoir XVI. Dr ore ie sie ary Lao M‘Parlane & Erskine, Lith Edin?