LIBRARY OF I885-I056 CASSELL'S NATURAL HISTORY EDITED BY P. MARTIN DUNCAK, M.R (LOND.) F.R.S., F.G.S. PHOFF.SSOn OF OEOLOGY IN AND HOXORARY FELLOW OF KINo's COLLEGE, COHBESPONDENT OF THE ACADEMY OF NATURAL SCIENCES, PHILADELr Vol. V. ILL USTRATED CASSELL AND COMPANY, Limited LOXDON, P.iniS & MELBOURNE 13D6 PISCES. PROFESSOR H. G. SEELEY, F.R.S., F.G.S., etc. INVEETEBEATA (INTEODUCTION). PROFESSOR P. IMARTIX DUNCAN, M.B. (Loxd.), F.R.S., F.G.S,, etc. MOLLUSCA. HENRY WOODWARD, LL.D., F.R.S,, F.G.S., etc. TUNICATA. HENRY WOODWARD, LL.D , F.R.S., F.G, MOLLUSCOIDA (BEACHIOPODA AND BEYOZOA). AGNES CRANE. INSECTA (INTEODUCTION). W. S. DALLAS, F.LS. COLEOPTEEA. 'IL W. BATES, F.L.S. HYMENOPTEEA. M'. S. DALLAS, F.L.S. C O : ,,.,■ (V|,.„lr. T. . tli 1 J:,ws- The Brancliial Ar-ches— The Muscles nf iM-lir^ Tl,. -^^. ...i M,. ■ - •, , T. i • i , : , :■, . i,,,,,- of Fishes is Due -The Scales of Fislies Auassi./v i I:,..!',. , ,.. i., - ., - ' I - , i Spinal Cord-The Krain-Orgiins of Si.ii-ll, s^l.t. ,n„l ll.,i,,i,, 1,,. l.l-.i,-. ~<, _..,,- I... [..il, ,.i l,.;,>. The Alinientaiy Canal— The Liver— The .lu-l.hul.kr Tin IJ.iu.l il.v Ikaii The l.ill.. liu., .u..l u,wi 1 uhctious - Chissilication of the Fishes .................. 1 CH.\PTEE II. THE PAL.T-ICHTHVE.S, OU FI.SHES OF ANCIENT TYPES. DIPNOI, OR MUDFISHES— Why this Order is Interesting— The African Mud-pish— Thk South American Mudfish— The Genus Cekatodus-GANOIDEI, OR FISHES WITH BONY SCALES— The A5iiiD.E-.4))i/(t o(/(v«— The Bony Pike of the Nile- The American Bony Pike— Its Remarkahle Characters HOLOCE- PHALA— The Chimnn, „„ui^tn,s„ -The ("ioinK ( 'allr.rlirnrlnis TT, \i :TnsT()'\[ATA Tlir Shaiks ah.l Hays— Selachuii.hi Tin: I'.irr Shakk Its ll:il.:r- M- , ' ,- x i! ',i ■. r< ,•„,;, i-,, i itlnr Cimi :, T!i- Cnmraon 1|.' • I . r.,ii.,.,_|,.. ,u th, !;-•:, u),.:hi~ shark- I.. -i . . ,^ i •..ii^ ri,. •■s,,i s..||„ ,,, ■ Hal.its— M,<,> I. Tl,.. I.Krt.ir (1,^:,,,, clMrarr.'i- lltlhi l-'nniis- THERAY.S : |.,,\,, \(.~rii Si, MI. I'm i; -11:111 \[\\ Tin Shaoheen Ray 11. sri\,; l;\^- cr.iH-tli nf Us ■■S|iiin' \";,riniis Species- The CIK IN] >i;i isTI::i 'i'm. sn ik.imns ( 'Inuartns I 'aviare— Fishery CHAPTER III. the LorHOiiUANcHii.— the ANACANTHINI. Fislifs of tills (inlpv -Their < 'liaracters- The Triacanthinai- The Til- llstr:,ri,,„i Til- i;vi,iii.Ml..nteS"-The Genus Triodon-Tlie fi-.i.li.hs Til- I -1111. l>aM-ii Harwin on the Habits of a Diodon iii,i-u Sin, ti^li-llalat^ I'li.u i-t-rs-Tlie Ohlong .Suu-tish— THE riir-~ Ttii s-l-ii-st-nia t'liara-ters— The Syngnathidie — Interest l>-srn,,tioii- I'lic (>;reat Pipu hsh- Hal.its— The JIarsupial Pouch W-iii, I'i].- tish-The Sea-horses— Phyllopteryx— Dr. Gunther's ;-iin. Ililil— aiui.us— The British Sea-horse-Other Species— THE I'm i'..|i Its \ ciraoity— Its Fecundity Tame Cod — Description of Hand Till- Flsliiii'4 -The HAimn-K A '"Ci-at ( '.mcliologist "— " St. i.tiii--T)ie Polliifk T'h- c.al iMi Tin 11 Mil" The Greater Fork !i:i, .MiniiK - Th- Silv-iy (--1. I'li- l;-rkllii-s Th- Tadpole Hake -TiiM (Jkxis 1''ii:i:asi'ei; 1 Msrln-tiw- l''-atur-s The Greater Sand I. 01; Tij-a la.xn tiii.K n,a,;,rt-rs-TnK Hoi.inrr - The Largest -sia-k-r The Ti i:i:-r Tin i;i;ii.i. -The Whiff, ok Mary Sole, OR Sail-flike— The T-|.kii-t - l;i ■ " ii's Tmi'knmi- Th- s^aM tisli. or .\l--rli.i. or Smooth Sole— The Genus Pleuroneetcs-THE 1'eai. 1 - I■a^-olll it- Fish of th- IV.or- La— |.-d-s Ston al.out Sliiimps and Plaice-THE Dab, OR Saltie, oh Salt-wateh Flike— The Smear Dab— The I'ule, or Ciaig Fluke— The Flolniiek— The Sole —The Lemon Sole— The N'ariegated Sole— The Solenette— Trawl Fishing 48 CHAPTER IV. the 01 nrus lirilW CMTHI and \ClNTHOFrERY II P mvcen TRID E— Distribution— Diet— Distinctive Featuies — -The C 01 kwmg— Other f>cneia— The Gioup fheropmi The Ci ,, T d Im i Tl 1 11 1 h W 1 1 e-TlR(inn Pstudoda\-The (.loup Seiiina-The Group OJvcini- Thi r Tii (FiRiit Th i -fhe Older At \NTH0PTEP\GII— Dr < unthers(l 1 11 i — The I 1 1 A\ 1 i I I) et— I aige sized S] ecimens Chuacters The Pis Tl 1 n The Sm tl s II lUi ky Perch-The Stone Liss 01 A\ leck hsb — A\Ti} so t 11 1 uil 1— Tir s 1 t IS Marion (meii tunusHilitof Shootm, at h 1 1 1 -The All liii I 1 M ln— 1 h 1 II 1 I 11 I I \ I !iNi -The M t -\ si s \l I M \ t^ M 1 1 I lis; nish Mickeiel-The Tiling— ( i viacteis— Size— The Tunn> Hll■^Lst -leef like 1 lesh— The Lonito— ih ( crmon— The Oenus Pelamjs-The Gen is Auxia— The Pilot hsh- The Sicking fish, or Kemora— Nature of the Sucking Disc 74 British Top--' I'm: H \M Ml 1; III MiEn Sii TheThremii i:. o|; Ko Tl i'i" n;K '1 Ml \'.y Fishen-s 1 h:ii Their !■;-,. :,,- v.- 1.1, ,,, ■ -Why so N:ih i-.j 1I 1-1 Industry kA'l' 1 111 : l:A^■s 1-- NIP.E-Tlll ill • ,1 ~ To] ;ri ■ Str-ii-tli of ih, -Characters-'] riie Tri u- Sk at--F.sT-rv- Th -The Homely I'm ; Thoknisack -T E.VGLE Kay-Ti IE 0\ 1; \V o.i Sea Den ■II.- —Other Ecoiion lie l•se^ Th e Common Sti '"='- TH IE PLECTOGNATH I.— PLECTOGNATHI-Si: ll"l ula r Shapes of tlie Balistin;e-The File-fi: Sh '1 'li- Mona-aiit liill: Globe. fishes -The Gen X, ■noiil-nis Th - T —Allied Gene ra— Th< Sii 11 lish-s Tll- 1 , LOPHOBRAXCHII- Th -ir distm-tn- I'-i attaching to tht •m-Th - 1 h-o ad nosed fip- -fisi, —Other Sptcii ;s-Tlie le- ,u. Pipe Hsh -Th Account of its Spines nd Fdaments - T ANACANTHIXI-Th i^-._ the Fish— Th- ( 'od-fish -ri Lon- Tin- an li ¥ Peter's Mark ' -The \V nil 'INO— Coueh's w Beard -The Bu rbot-'l Tii .: 1 .1x0 -The .M. II'KI —The ToitsK- -The 1 Oil lii, liida--('liarac ters Eel-The Less d ]■:, ■1 The Fevt -Els of the Flatlis ih — Th lii s.,11 jv XATVRAL HISTOKY. CHAPTER V. ORDER ACAXTHOPTEUVGU (coildudcJ). Pi The Trachinid;e— Uranoscopus— Star-gazers-The Greater Weever, or Sea Cat— The Lesser "Weever— The Malacax- thidj:— The Batbachid.e— The Pedicllati— The Sea Devil, ok Angler— Its Voracity— The Genus Malthc — -CoTTiNA— The JIillek's Thumb, ob Eiver Bullhead— The Sea Scurpkjn, or Father Lasher— The Gurnards— The ('ATArHKACTi— The C0MEPHORID.E— The Discoboli— The Lump-sucker, or Luinp-fish— The Sea- Snail— The (Jcbiid.e —The OxuDERCiD^E- The Cepolid.e— The Trichonotid.e -The Heterolepidina-The Blenniiu.e— The M'olf-lisli, or Cat-fish— The Butterfly Blenny— The Shanny— The Viviparous Blenny— The Acanthoclinid.e— The Mastacembelid.e- The Sphyr.enidj:— The Atherinid.e— Tlie Saml Smelt— The JIi'GiLin.E— The Grey Mullet— The Gasterosteid.e— Sticklebacks— The Three-spined Stickleback — Its Pugnacity- The Nest— The Ten-sjiinerl Stickleback— Tlie Nest— The Fifteen-spined Stickleback, or Sea Adder — The Nest— The Fistularid.e. or Pipe-eishes— The Cextriscid.e— The Trumiiet-fish, or Bellows-fish— The CHAPTER VI. the order phvsostomi. ORDER PHYSOSTOMI-Silurid.e— Characters— The Various Sub-Families— The Silurus Glauis— The Malapterurus electricus- Its Electric Organ— The Genus Loricaria— Curious Feature connected with the Genus Aspredo— ■ t'HARACiNiD.E— Hapliichitiixiii.e— Stern'optychid.e — Pearl-spotted Fishes— Scopelid.b— Bombay Duck— Sto- miatiii.e— Sai.moxid.e -('haracters— The Salmon — Description — Climbing the Rivers— The "Leaps" — Changed Appearance after Spamiiiij;— Hatching— The Fry— Growth-Stages of the Young— The Journey to the Sea— The Salmon at Sea— \'arious Jlodes of Fishing— Largest Catches— Distribution— The Grey Tbout— The Salmon Trout— The Cosniox Trout— The Great Lake Trout— Other Species of Trout— The Charr— Various Species— The Smelt— The Capelan— The Genus Coregonus— The Pollan — The Grayling— Percopsid.e— Galaxid.e— Mormtbid.e— Gymxarchipe- EsociD.s— The Pike— Its Size and Age— Its Voracity— Pike Migrations — The Lucie Family— Characters of the Fish— Ujibrid.e—Scombresocid.e— The Genus Belone— Tlie Garfish—The Genus Scombresox— The Saury, or Skipper— Tlie Genus Hemirhamphus— The Flying Fish— The Genus Exoccetus — Characters— Height and Dur.ition of Flight— CYPRIXODONTID.E—Singxilar Eye Cliaracter of Anableps— Heteropygii —Cyprixid.e— Distinctive Features -The L'arp— Habits -Carp Culture- Its Diet— The Crucian Caqi— The Golu Fish- Kept as a Pet— Variation in Colour-Characters— The Barbel- The Gudgeon— fhe Roach— The Chub-- The Dace— The Ide— Tlie Red-eye, or Rudd— The Jlinnow— The Red-fin— The Spawn-eater— Tlie Tench— The Rhodeus amarus — The Bream— The Bleak — The " Essence de I'Orient " — The Loacli — The Spinous Loach , . 107 CHAPTER VII. phvsostomi (concluded) — CYCLOSTOM.ITA — LEPTOCARDII. Gonokhynchid.e— HvoDONTiD.E— Osteoglossid.e-Clupbid.e— The Anchovy— The Herbing— The Fisheries— The Boat and Nets— The Whitebait— Tlie Sprat— Tlie Shad— Tlie Pilchard— The Pilchard Fishery— CHIROCENTRID.E — Alepocephalid.e— Notopterid.e— Halosaurid.e— Gyhxotid.e— The Electric Eel— Electric Organ- Effects of the Shock— Sv.mbranchid.e--Mur.enid.e — Characters— A'arious Types— The Shabp-xosed Ee'_,— Weight — Habits - The Broap-xosed Eel— The CVixgeb Eel— Characters— PrehensUe Power of its Tail— Habits— The Genus Mur:ena-PEi;Asiii.E-CYCL0STOMATA—Characters—MARSIPOBRANCHII—PETROMYZONTII>,E— Characters— The Sea Lamprey— Distinctive Features— Great Suctorial Power— Distribution— The Lampern, or River Lampkey— The Saxd-piper—Myxinid/E— Characters— The Hag —Distinctive Features— Remarkable Nostril Character —Its Enormous Mucous Secretion— LEPTOCARDII— CiRROSTOMi — The Lancelet— Size— Characters- Peculiar Heart and Blood -Difficulty connected with it and Hag— FOSSIL FISHES IM THE ANIMALS WITHOUT BACKBONES— THE INVERTEBRATA. INTRODUCTION. Characteristics of Vertebrata— Modifications— Characteristics of the Invertebrata— Various Distinctions among Theni- -Habits — Classification — Intermediate Group INVERTEBRATA.— TYPE MOLLUSCA. CHAPTER I. the cephalopoda. Cephalopoda— Derivation of the Term— Unexpected Relationships— Shells- -Utility of Aquaria— General Characters of the " Naked" Ceplialop()ds--('lassiftcation : tlie Dibranchiata and Tetrabranchiata— Their Mode of Locomotion— Tlie Moutli anil Eyes— Jleans of Escape and Defence— Representative Dibranchiates im the Ancient World— DIBRANCHIATA, OCTOPOD.V-ARGOXArTIIi.E- The Argonaut, or Paper Nautilus— Its Fabled Position— Its Praises as Sung by the Poets— How the Nautilus re.ally Swims— The True Uses of the Arms— Curious Fact regarding the Shell— The JIale as Conii>ared with the Female — Tlie " Hectocotylus '"—Species of Argonaut— OcTOPODIIi.E— The Common Octopus— Ajipearaiice— Formidable Seizing Organs— Owen's Description of the Tentacles— Mechanism of the Suckers— The Octojiods of Leghorn— The Octopus of tlie Greeks— Mr. Darwin's Account of the Octopus— A Diver Attackeil— The Adventures of an Ocf&pus in an Aquarium— Spawning Season — Eggs of the Octopus— Henry Lee's Observations as to the Hatching of the Eggs— The B.aby Octopus— New Grewth of Amjiutated Limbs— Food for Predatory Fishes— Contests with the Conger Eel— Tlie " Devil-fish " and Nursehouud- \'aiious Species of Octopus — De Montfort's Gigantic Octopus— Cuttles and Octopus as Diet —Octopus Fishery— DECAPOD.V—Teuthiii.e— Distinctive Features— The Tentacles— Suckers— Shell— Remark- able Skin Char.irteis-Tlay ..f C.,l.,urs— THE CoMMOU SijuiD—'Ten-and-ink Fish "—Their Spawn— Tlie "Little Squid- " Tlir N, n.- i.-'s, - „f the Dibranchiata— A Tom Tbimib (\-y\rA„i»u\-- L„i:,i..r>-is-ri„ iruln.lhh- H, t:<.l,,'t>>, I'l,,, ( l,«.a ( .l,ai, ,1V— Construction of the Suckers ,.f tli.' Calamarv Tl»- .\nnr,l C:,lain:irv— Tlie Sa -itt.it, il ( ,il Ml, I.N ■• ,S. ,,-anws "-Squid-bait-The Cod-tisherv- Sn„i,l-,i^.,-i,iu Tin- (;iant ( 'rphaliipoils -Ii,.-t,iiie, . i,t tl,. 11 li. iii^ Mit null, and of their Capture— Sir Francis rl, ant ivy ami JV.ssil Ink- l;i.LEMMTin,K - No Lining Repicseutative \\liat the Fossil really is— Species— Sepiaij.e— The Commoii Cuttle-tish— Beautiful Coloration— The Bone or Shell— The Cranial Cartilage in the Cuttle— The Heart— Movements in the Water— Not Long-livctl in Confinement, ami why— The Cuttle's Eye— The " Ink-bag "—Discharge of the Ink— I^se of the Ink— The Eggs of tlie Cuttlu -Young CuttUs Tsrs of the " Bone "—Various Species of Sepia— The Cuttle as an Article of Diet— Siii:i iii.i Cim;, Spiinla Kiiuarkable Characters— Rarity— DiBicuIty of Studying it— Peculiar Shell ('liaiaii.is oliliKK li: I'l; A] '.KAM illATA—NAlTILIAD.E— External-shelled Cephalopoda— Nautilus and Spirula tin.- chlIv Siiihuiiiit.il SluIN I.iviiiy -C!onstruction of the Shell— Rumpliius's Account of the Peariy Nautilus— Jlr. Musclcy's (_)bsL-rvMtioiis— How tliu Animal Moves— Abundance- Various Parts of the Nautilus —The Air-chambers— The L'ses of the Sipluincle— Formation of the Septa- Fossil Members of the Tctrabranchiata 1")4 CHAPTER II. THE GASTEROPODA. " Shell-fish "—Uses of the Shell— The Kinds of Shells— Economical Uses of the MoUusca in the Earliest Period and in the Present Day— Form and C.rowth of Shells — Parts of a Shell— Order I. PROSOBRANOHIATA : (a) SIPHONOSTOMATA— Siphonated Gastero;ioda— Family I. STROMBID.E, " Wing-shells "—2. MuRICID.E— Murex, the Source of the Celebrated " Tyrian I'urple ' Dye—" Mitre-shelk " — Fuaus, the " Red Whelk " — Whelks used for Food— Hemifusus, one of the Largest of Living Shells— ;i. BucciNlD.E-Buccinum, "Triton's Shells" — The"Dog Whelk," Nassa— Purpma— Its Dye -How it Tackles its Prey— Magilus Boring in Coral— The Haqi- shells— The Olives— 4. Cassidid.e— Cassis— "Cameo-shells"— Triton— Use of the Sheilas a Ti-umpet- Growth of Sea Snails— 5. CoNio*— The " Cones "--Their Beauty and Commercial Value — Conus Gloria-maris— Terebra, the " Auger-shell "—6. Volutid.e— Rarity of the Volutes— 7. The CvPBJiiD.E— Cowries— Richness of their Colour and their Value— Past and Present Prices of Specimens of Rare Shells — The Money Cowry— Cuttle-fishing with Cowry Bait— Shells as Articles of Ornament in Dress— Ovulutn ISa CHAPTER III. THE GASTEROPODA (condiuiici) AND PTEUOPODA. Order I. (coiicl iidec[)—{h) th^ Holostomata, or Entire-mouthed Sea Snails— Family 8. Naticid.e— 9. Canxellarjad.e- 10. PvRAMIDELLIt>.B— 11. SdLARiAD.E -"The Staircase-Shcll "—12. Scai.ari.'vd.e- Scal.iria pretiosa, the " Wentle- trap "—Great Value attached to this .Slicll- i:l CERITHIAD.E-Potamiiles in Fresh AVater— 14. Ti'RRITELLIO.e— "Tower-shells"— Vermetus—Worni-shcUs— 1.1. Melaniati.e— Hi. Paludinid.e— Fresh-water Snails— the " Apple Snail," Ampullaria— Its Tenacity of Life— 17. Littorinid.e— Periwinkles as Food— 18. Cai.vptr.eid.e— "Bonnet Limpets"— The Grotto-shells, Phorus -lit. Tlrbinid.e— Trochus- 20. Haliotid.e— The Ear-shell, Haliotis— Uses of Pearly Shells— Pleurotomaria— Its Rarity— 21. lANTHiNIDyE— lanthina, "Floating Shells'— The Katt— 22. FlssiRELLID.E— 23. NERITin.E -24. Patellid.e— "Limpets"— Used as Food— How the Oyster-catcher Detaches them-25. Dentaliad.e— 26. CHITOXID.E-Jlultivalve Snails— Order II., PULJIONIFEKA-.\ir-breathers— An.atomy of a Snail — Inopeiculata, or Land Snails without Operculum — Characters — Curious Experience of a Desert Snail— 27. HEi.Kin.E — Usr.l as Food— The Largest Land Shell Known— The Odontophore, or Tooth-bearing Tongue -Other (;enera-2S. LiMACiD.E— The Slugs-The Mucus Secretion and its Uses— 29. ONCIDIAD.E— 30. LiMN-EiLi.E— Air-breatliing Pond Snails— 31. AuRICULlDiE -Operculata,orOperculated Land Snails— 32. CvcEOSTO- MiD.E-33. Helicinid.e-34. Aciculid.e — Order III., OPISTHOBRANCHIATA— 3.5. Torn.\telhd.e-36. BuLLiD.E— 37. Aplysiad.e— " Sea Hares" — 38. Pleurobrahchid.e— 39. Phyllidid*:— The "Sea Slugs"— 40. DoRiD.E — 41. Thitoniad.e — 42. .Solids- 43. Phyllibhoid.e — 44. Ely.siad^— Order IV., NUCLEO- BRANCHIATA-Oceanic Snails-4o. Firolid.e— The 0'arinaria-4(;. ATLANTin.E-Class III., PTEROPODA —Their Pelagic Character— Their Abimdance— Source of Food to the Right Whale— Their Wing-feet compared to Moths— Delicacy of their Shells— Distribution 207 CHAPTER IV. the conchipeka. Class IV., CONCHIFERA— Bivalve Shells— Their Sedentary or Burrowing Habits— Structure of Bivalve Shells - Anatomy of Animal— Muscles, Mantle, Gills, &c.— Family 1. OsTREID.E— Oysters— Then- Economic Value- Frank Buckland on the Oyster— The "Points" of an Oyster— Mode of Cultivation — The Young Oysters— Their Enemies— Their Sensitiveness to Cold— Ancient Shell Relics— 2. Anomiad.e— 3. Pectinid.e- Scallop SheHs— The St. James's Shell— The Spimiliilm, or Thorny Oyster— Vivacity of Young Pecteu— Value of Bivalve Shells— 4. Aviculid.e— Peari Oysters— Use of Shells— A'alue of Pearls— Pearl-fisherj', Ceylon— The Divers— The Gre.vt Pin.va — b. Mytilid.e — JIussels — A Bridge Preserved by JIussels from Destruction — Boring Shells, Lithodomi-6. Arc.\d.e-7. Tricoxiad.e— Trigonias— S. Unihnip.e -River Mussels-Peari Mussels— 9. Chamid.k — 10. Trid.^CNID.E- Giant Cl.ims -11. CARDiAn.K -12. I.rtiMD.E i:!. Cvi lAniD.K— 14. AsTARTID.E — 15. Cyprinid^— 16. Venerid.E- 17. Mactrip.e- IS. TEi.i.iNin.E— 19. Soi.emI'.e ■■ Razor shells"— 20. Myacid*- 21. Anatinid^— 22. Gastroch.enid.e— Stone-borers- 2H. I'hcii.aihh.e— Wood Ixuers— The Ship-worm . . 230 INVERTEBRA.TA.— INTERMEDIATE TYPE. THE TUNIC AT A. Structure of the Tunicata Explained— The Throat or Gullet serving as the Breathing Organ— Curious Ebb and Flow of the Blood — Their Division into Simple, Social, and Compound Ascidians — Known to Aristotle — 1. SmPLE AsciDiANS — Muscular Nature of Tunic — "Sea-Squirts" — Where Found — 2. Social Ascidians — Mode of Union — Genera— 3. True Compound Ascidians— Theii- Anatomy— 4. The Pyrosomid.e— Their Pelagic Habits— Their Phosphorescence — 5. Salpid.e— Pelagic— Solitary or in Chains 2.")£ THE INTERMEDIATE GROUP, MOLLUSCOIDA. the M.ANTLE-nREATHING BIVALVES (bRACHIOPODa) AND THE MOSS AXXMALS (bRVOZOa). THE BRACHIOPODA— Life History and Characters of the Brachiopoda— Origin of the Name— Subdivision of the Group — Its Relations to other Organisms— Growth and Structure of the External and Internal Skeleton — Muscles— Organ of Attachment— JIantle— Gills — Digestive, Generative, and Nervous Systems— How the Brachiopoda Live -Classification and Anatomy of Jlinor Groups — Distribution in Space and Ranges of Depth of Living Forms— Fossil Genera -Eml.iyology and Affinities— THE BRYOZOA— Life History of the Moss-animals —Name and Position of tlie i .y.uy Its Chief Subdivisions— The Colonial Skeleton— The Indivi.lual Aloss-animal — Muscles and their Aetion -li's|arat<>ry, Circiilatox'y, and Reproductive Systems — Structure and Functions of the Appendicular Organs— (_'lassitieatinn and Anatomy of Alinor Groups — Geographical and llatliymetrieal Dis- tribution of Marine and Frcsli-water Genera— Geological Range- Reproduction of the Colony and of tlie Indiviilual ^Embryological History— Affinities and Systematic Position of the Brachiopoda and Bryozoa . . . 2J8 NATURAL HISTORY. CLASS INSECTA. CHAPTER I. ANATOMY OF INSECTS. Characteristics of tho Arthrn ipnila -Insects ^Division-, of the F.o.lv Se-meiitf . of thf — The .lnil.tr, 1 l.iliilis- \j-A- Tl,.' I'.-.-t Til.' -Win-s Tl„. 11.-.,. 1 MoUth- ,S,,;„,.„,,;thin 1 ,.f tl,. 11>. ..1 -M...l,lic;,tl..ns .,f tl... M..llth The ■■T.;,l,4nnn:,tlM„ . -.if ll„.'Ct>: l.a.va, I'ui.u. an.l \V,„-,,.l St;,:;es Inter; — Structuiv .if thr V.y: iM.iicti.. 11 of the Alitelilue-The Dl-e.tl How Ke.si.iratioii is 1', .■rfurme.l— Kej .ro.luction— Classification . CHArXER 11. OKDEll COLEOITIiHA :— I AUMV.H Definition of the Order— Functions of the Coleoptera in N:.tiii.> Structure —Metamorphosis and Early Stages— Instincts \'..ii . .imin- ami Organs of Hearing the Haunts of the Majority of the Species of Coleojiteia Xoetuiiial Habits — Attracted by Light — The Number and Variety of Species swept down by Floods in River-valleys -Fossil Beetles— Section Pentameba, Beetles with Five-jointed Tarsi— Tribe Adephaga, or Predaceous Beetles— Family Cicindelid.b, or Tiger Beetles — Family Carawd.e, Carnivorous Ground Beetles \ CHAPTER III. CAKXIVOHOl'S, ANOMALOUS, AND BVRYING-BEETLES. Pentameh.v (r„»/(«»(i/l --Family Hvncni.K, or Carnivorous "Water - Beetles^Air-breathing Insects— Peculiar Mode Type ..t -I .'•!. 1 !. ■ : - \' . ■ \ ,.ii.' 'I';: -■• . ■! I ' I I'l',.: I'-."', li I'ets ..f Ants- Tribe NECKorii ■ . . . I ■, , '. ■ , i I . ;._.'.■; ; , ,, ,■ :i I, •■ ; ',' I ; ! 1 . h. - ii 1 1 . i: r.iirying Beetles, and tleai ^11. -ill, II il.ii.i;- ImiiiiIi.- I'i: i. h. h- 1 ; i. i . . ii > i,. -.. Mii 1 1 1. i . ■ i . Ti. .\ l.m i, i i ■ i.. aii.l Xi rii'>ui,iP.E— The Smallest IJeelle^ kll.,uu l-ali,llK-> Tii.Ji,.»lUl..t to ;il.-lhhll..L-l^n,U.l the Xeeiupliag;. CHAPTER IV. THE LAMELLICORN AND si;i;l;I(01!N- r.Er.TLES. Pentameea (mH 1 — Tl WalM\ i-TheCrb -Tl lA i -The Po p e Th The F R e or ANTS-Cha at -Tie Ne t -The M t ilo T\ \> Chaige of the \oung-Habits-Intelligence-The -Wood Ant-Othei Species- Th Wasps -Th -\I - k -Mdk tl Apl 1 - K CHRlMiniDiE, (IR GOLnE^ . . . . . .353 LIST OF ILLUSTEATIOIsrS. The Blue Shark ... The Common Pike Skeleton of the Common Peiuh Skull of Codfish . Scales of Fish Diagram of Brain of Coilfish . Jaws of Male anil ot Female Skat. Internal Anatomy of the Oar]) Swimming Bladder of Carp . The African Mud-fish . The Ceratodus The Polypterus A Vertebra of the American Eon Chimajra CoUiei . Diagram of Brain of Skate . The Hammer-headed Shark . The Smooth Hound The Nurse Hound Egg Purse of Nurse Houu,l . Egg of C'estracion ; Section of tht The Picked Dog-tish . TheMonk-tish Tlie T. Tlic Tl Tet :-fish Tl.e Phylloi.teryx . The W'ldting . The Usser Sand Eel . Tlie Turbot . The Plaice . The Rainbow Wrasse . The Epibulus Insidiator Tlie River Perch . The Bass The Toxotes . The Pelor filamentosum TheMaigre . The Common Sword-fish The Flying Sword-fish . The .Jolm Dory . The Opali The Pilut-fish The Suekiim-H.,h, ur Ren Tlie Se Tlie Ar Tlie Buttertiv lUeiinv . The Ten-spineil Sticklebacks . The Fifteen-spiiied Sticklel>ack The Trumiiet-tish, or BeUows-tish The Climbing Perch . .Supra branchial ( >rgan of the Clir Loricarja i:ataphracta . Tlie Cu 1 Trout uelt The Grayling The Garfish . The Exocoetus volitans . The Crucian Car]! . The Roach . The Tench . Rhodeus amarus . Vertebra of Herring The Herring . The Sprat The Conger Eel . The Pegasus Draconis . 14* The Sea Lamprey 144 The River Lamprey 14."> The I.ancelet 147 Tongue of the Octopus l.">.") Fabled Position of the Paper Nautilus .... 1.5(; The Paper Nautilus and the Octopus . To face imyc 157 Argonaut as it Swims Backward (Natural Position) . 157 Paper Nautilus in its Shell 157 Cross Section of Arm of Octopus — Suckers of Octopus . 158 The Common Octopus 159 Octopus horridus— Octopus macropus . . . .160 The Common Octopus . . . . Ta fare pui/e Kil The Octopus Reposing ....... 162 The Pinnoctopus— Cirroteuthis Mulleri . . . 1()4 The Common S.iuid 107 Buccal Aspect of Common Squid— Loligopsis . . 168 The Pen of the Calamary KW Gigantic Cuttle-fish Hooked off Teneritfe . . .172 Upper and Lower .Jaw of Architeuthis nionachus. . 173 Marginal Ring of Sucker from one of the Sessile j\j-ms of iVi-chiteuthis monaclius. Large ami Small Sucker from the Tentacular Arms of Same. Larger Sucker from Tentacle of Same .... 173 Belemnite Restored ....... 175 The Common Cuttle 176 Branchia; and Hearts of Common Cuttle . . . 177 Sepia elegans 178 EgKS of the ( 'ommon Cuttle-fish— Shell of the Sepia , 180 Section of Spirilla Australis l."l Spirula Au^trali,- 182 Interior of the Shell of the Pearly Nautilus . . .185 Exterior of the Shell of the Pearly Nautilus . . 186 Section of the Shell of the Pe.arly Nautilus . , . 186 SheU of Triton 191 .Strombus gigas, with the Animal — Pteroceras lambis . 192 JIurex tenuispina-^Mitra episcopalis . . .' . 193 Fusus proboscidalis .194 A Group of Sea Snails — Patella vulgata ; Buccinum undatum : Nassa reticulata ; Haliotis tuberculata ; Littorina littorea 196 Purpura lapillus-Puri.in-;. pntiil:, . . . .197 Blagilus aiitinuus- Il;ii |i:i i!niMri;;!is Harpa articularis 198 Olivaerythrostoma - olna pMiplivna 199 Ca.ssis eaiialieuLitiia— Cassis iiKi.lagascariensis . . 199 'JMn.l, >:,nru,,I,|l„ 200 r,^ . ^ i \ . I i,.s . . . . T.i fare jxiqf 201 'i'^ :. I.i -.•!. " . .201 Th, I u:, n- i( A ,„,ea tigi-is) and its Animal . . . 203 The Jlouey Cowry 204 Cowries .......... 205 Ovulum volva 206 Natica papilionis . . . . . . . .2)7 Solarium persiiectivum— Scalaria pretiosa— Cerithium aluco 209 Turritella terrebellata -Vermetus lumbricalis . . 210 Melania amarula — Lingual Teeth of Ampullaria— AmpuUaria canaliculata ...... 211 Phorus conchyliophorus— Turbo argyrostomus— Turbo imperialis 214 Troohus niloticus— Trochus vir.gatus — Haliotis tri- costalis '. . . 215 Pleurotomaria quovana riiuintumaria platyspira . 216 lanthina communis liiiitlni imI its Raft. . .217 Dentalium elephaiitiiiimi i Intm, magnificus . .219 Anatomy of the Common Garden Snail . . .220 Land Snails Tn fair paye 221 Helix pomatia " . .221 Lingual Teeth of Achatina fulica _ . . . .222 A Slug. (Arion ater, " Black Arion") .... 223 Lingual Teeth of Testacella haliotides .... 223 Limnsea stagnalis— Physa castauea .... 224 NATURAL UISTOIii'. Cyclophorus, an Ojierculated Land Snail . . . 225 Bulla oblonga—Aplysia inca— Shell of Aplysia inca . 225 Iilalia ; Mii-ancla : Dendronotus ; Doto ; Hermiea ; Glaucus— Carinaria cymbium .... 227 Hyalea gibbosa— Hyalea longirostris— Cleodora ciispi- data~C. lanceolata— C. compressa . . . 229 Anatomy of a Common Oyster 231 Anatomy of Cytherea 232 Young Oysters furnished with Locomotive Organs . 234 Group of Oysters of Different Ages .... 234 Shells of Pecten and Spondylus . . To face patjc 265 Meleagrina margaritifera 237 The " Hammer Oyster " 238 Pinna nobilis, mth its Byssus— The Sea Mussel . . 239 Three Erect Coliunus of the Temple of Serapis at Puteoli bored by Lithodomi 240 Anatomy of Trigonia pectinata— Trigonia costata — Trigonia pectinata 241 I^nio pictorum — Anodonta eusiformis .... 242 Tridacna squamosa 243 Cardium edule ; Cardium echuiatum ; Jlya aieuaria ; Cytherea chione 244 Venus verrucosa, with its Animal — Cytherea geogra^ phica, mth its Animal— Cytherea maculata . . 246 Tellina radiata 247 Donax trunculus— Solen eusis— Solen vagin.-i . . 248 Anatomy of Soft Parts of Mya arenaria . . . 249 The ■\Vatering-pot Shell 250 Pholas dactylus in a Shelter— Teredo navalis . . 251 Structure of Tunicate 252 Cynthia (Ascidia) miorocosmus 253 Boltenia (Ascidia) peduu:;ulata 2.54 Pyrosoma 256 Salpa maxima 257 Terebratula cubensis— Disoinisca lamellosa . . . 258 Rhynchonella spinosa ; Productus longispinus ; Cho- netes ; Ventral Valve of Productus complectens . 2.59 Sections of Shell Structure . . _ . . . .260 Ventral and Dorsal Valve of Waldheimia australis . 261 Ventral and Dorsal Valve of Lingula anatina . . 261 Dingula pyramidata 262 Animal of Lingula anatina ...... 263 Crania anomala 264 Internal cast of Dorsal Valve of Orthis ; Section of Pentamerus, showing Chambers — Dorsal Valve of Spirifera glabra ; Dorsal Valve of Khynchonella psittacea 205 Loop of Liothvi is : Terebratulina ; Terebratella ; Bou- I'liiiraiiL ; '.Mr-^rrlia ; Argiope 266 Theci.lniin i!i,i,f,,n;ineum, asinLifc . - . .266 Terebratula Wyvillii _ . .267 Free-.swininiiiig t/iliated Larva of Terebratulina; At- tached ; Later Stage ; Horse-shoe stage of Loop . 2CS Bugula purpurotincta ....... 269 C'ristatella mucedo ....... 270 Winged, Crescentic, and Circular Type of Gill Tentacles 273 Alcyonidiiim gelatinosum ; Plumatella allmani . . 272 Cell and Anatomy of a Moss-animal .... 272 Moss-animal Retracted in its Cell .... 273 Communication Plates and Pores in CeH Walls of Membranipoiu membranacea ; Perforated Stem of Zoobotrj'on — Alimentary Canal of Cellepora. . 274 Cells of Cheilostomatous Bryzoon— Portion of Poly- zoarium mth Vibracula; ; Sessile and Pedunculate Avicularia — Cells of Bu^ida avicularia, with Avi- cularia holding a Worm 275 Stomatopora dichotoma 276 Bowerbanki.a— Endoproctous Type, Pedicellina cernua 277 Free-swimming Ciliated Cheilostome Larva ; Statoblast of Fredcricella 2-SO PABB A Beetle with the Head, the Portions of the Thora.\, and the Abdomen Separated and Magnified . . 281 Side View of Abdomen of Decticus .... 282 Walking Leg of Cockroach 283 Head of Hornet — Various Forms of Antennie . . 284 Organs of the Mouth 285 Earwig in its Development 288 Larva, Chrysalis, and Imago of Papilio machaon. . 289 Nervous System of Larva of Bee ..... 290 Nervous System of Perfect Bee 291 Structure of Eye of Cockchafer 292 Digestive Apparatus of Dyticus 293 Coleoptera Escaping from a Kiver-flood . . . 301 Cioindela campestris and Larv.e :J02 Phreo.xantha klugii 303 Carabus auratus 304 Carabus adonis ........ 305 Procerus gigas — Damaster blaptoides .... 306 Mormolyce phyllodes — Tefiius megerlei. . . . 307 Hyperion schrceteri — Anthia thoracica .... 308 Dyticus marginalia 310 Huliplus fulvus — LaccophUus variegatus— Hydroporus griseostriatus— Suphis cimicoides .... 311 Enhydrus sulcatus — Gyrinus distinctus . . . 312 Hydrophilus piceus 313 Ocypus olens (Devil's Coach-horse) and Larva . . 315 Pselaphus heisii 31G The Burying-Beetle . 318 Dermestes lardarius and D. vulpinus .... 321 Cerambyx heros and Lucanus cervus (The Stag Beetle To face imye 324 Dorcus titan 324 Sacred Beetle 325 Cockchafer 327 Xylotrupes dichotoma — Megaceras chorina:us . . 328 Megasoma typhon — Goliathus drui-yi ... . . 329 Ceratorhina polyphemus 330 Rosechafer— Cyria imperialis 331 Chalcophora mariana— Elater preparirg to Spring — Jumping Organ of Elater 332 West Indian Firefly— Alaus oculatus .... 333 Lampyris splendidula ....... 334 Meloe oicatricosus— Sitaris muralis .... .S37 Stylops spencei 339 Ehynchophorus palmaiiim 341 Ehynchites bacchus— Apoderus coryli .... 342 Larlnus maculosus. 343 The Stag horned Longicom . . . To /ace /m.vc 345 Oncideres vomicosus ....... 347 Crioceris merdigera 349 Liiia populi 350 Seven sp,.tt.-a La.lv bird 351 The Tail.Ml ^\•a^p 353 Dia-iain .if Hviii.i„,pterous Wing . . . .354 ComiiM.n Wasp - l.arvaof Saw-fiv 355 Larva, Nyiupli, and Cucoon cf Wood Ant . . .356 Head of Bee-Thu Hive Bee 359 The Honeycomb— Under Surface of Bee, showing the Wa.\ between the Segments 361 Apathus vestalis 366 Osmia leucomelana and its Nest 368 Leaf-eating Bees and Nests . . . To fair parjc 369 Mason Bee 369 Polistes g.allica and Nest ...... 372 Philanthus triangidum and Nest 374 Pelopffius spirifcx and Nest 375 Mutilla europiea 377 The Wood Ant ........ 37S ■ Myrmecocystus mexicanus 382 Sauba Ant .883 CASSELL'S NATURAL HISTORY, .^^^. Si CLASS PISCES.— FISHES. GEXERAL INTRODUCTION.— THE CHAPTER I. >rATOMY AND OTHER CHARACTERISTICS OF FISHES. Immense Variety of Forms— Characteiistics of the Class— Industrial Importance to Man— Fecundity— Colour— Mental Endowments— Their General Structure— The Lowest Type of Fish— Structural Features in Sharks and Kays -The Skull— Peculiarities in the Lepidosiren— Skull of Codfish— The Sense Capsules— Teeth and Jaws -The Branchial Arches— The Muscles of Fishes— The SMn and Mucous System— To what Causes the Colour of Fishes is Due-Tlie Scales of Fishes— Agassiz's Classiacation based on Scales— The Nervous System— The Spinal Cord— The Brain— Organs of Smell, Sight, and Hearing— The Electric Organs— The Teeth of Fishes— The Alimentary Canal— The Liver— The Air-bladder— The Blood— The Heart— The Gills— Fins and their Fimctions— Classification of the Fishes. FISHES are the only primary division of the Vertebrata which live in water, aiid have no repre- sentatives passing tlieir lives upon land or in the air. This condition of existence is probably the cause of the close correspondence in bodily form in the majority of fishes, which progress through the water chiefly by movements of the tail, and use the fins as organs with which to steer a jiath. Clear as is the idea which rises in the mind at the mention of a fish, the multitudes of forms which fishes exhibit are greater, perhaps, than those to be found in any of the preceding great 52i! 2 NATURAL HISTORY. groups of animals wliicli liave alreadj' been describetl. The slender iorm of the Lamprey or Eel contrasts with the expanded body of the Turbot or Plaice ; the short deei) form of the Sun-6sh is unlike the broad, flattened, and long-tailed Skate ; the Sea Horses, when attached by their prehensile tails, at first sight present none of the familiar characteristics of fishes ; the Flying-fish, wliicli have the fins so expanded as to serve some of the purposes of wings, present a remarkable contrast to the spheroidal spiny body of the Globe-fish ; while the Hammer-headed Shark exhibits a form of body in some respects more singular still. When we turn to details of proportion and structure, and contrast the shapes of the head or of the tail, the variety among fishes is altogether exuberant, lu the covering of the body there is not so much scope for variation, for although some are con- tained in a box of bony plates^ or mailed with armour far heavier in proportion than that of the knights of old, and some fishes have, on the other hand, scales so delicate that they are detected with difiiculty, yet by far the larger number of living fishes are clothed with soft scales, which impai-t to them much of their beauty, and difier in little more than size and details of ornament in the multitudinous genera. But beyond the claims ujjon our attention which the external forms of fishes certainly make, an interest of a far higher kind is always aroused by their wonderful habits. Here we find the herbivorous and carnivorous types of the land reproduced. Many fishes — like the Sword-fish, for instance — seem specially moulded into shape for purposes of slaughter ; many fishes, like most of those with transversely-expanded bodies, pass their lives more or less quietly on the bottom of the sea, and simulate the sand they re.st upon ; other groups, like Eels, dive into the sand as though it were their natural home ; others, again, like the Gurnards, crawl with their appendages at the sides of the head, almost like some of the Crabs, when they are not freely swimming. Some fishes, like the Sturgeon, find their home indifferently in fresh or salt water ; several, like the Salmon, require to descend annually from the river to the sea. Multitudes of fishes travel in fellowship year by year over a large portion of the ocean, a few fresh-water fishes journey over land, and one or two are sometimes found roosting like birds in the branches of trees. The industries which fishes have contributed to develop have given this group of animals an importance scarcely second to mammals and birds. No small proportion of the food of mankind is obtained by the fleets of fishing-boats around the coasts, and by the humbler nets, and snares, and lines with which fishes are captured in rivers and lakes. The use of fish for manure is of ancient date ; the capture of fishes for the manufacture of medicinal and other oils, gelatine, and isinglass is carried on on a large scale ; the skins of Sharks Iiave always been valued for the decoration of some kinds of military weapons no less than by the cabinet-maker for their ra.sping properties. Much of the artificial jewellery, which resembles pearls so closely as almost to equal the natural production of the sea-shell Avicula viargarili/era, owes its beautj' to a preparation from the scales of the Bleak and other fishes. The fecundity of fishes far surpasses that of any other group of vertebrated animals. The eggs laid by a single fish sometimes may be counted by millions. They are almost always small — as may be seen in the ordinary hard roe of the fishes which are eaten — and are frequently minute. They pass through no metamorphosis, as do the young in their development among the higher group named Amphibia ; but occasionally fishes are viviparous, and then the yoinig are i-etained within the body of the parent until they have reached a rejatively large size. Fishes furnish us with the smallest examples of the Vertebrates which are known, and also with some of the biggest forms, though they never make any approach to the giant length of the larger Whales. By far the greater n\imber of fishes are of relatively small size. As with mammals and birds, the great majority of fishes are characterised by comparatively dull colours, which probably serve to conceal them from enemies, and have been develo])ed as a means of enabling them to mimic the aspects of the regions of sea and river wjiich they frequent. Bxit all are not so simply decorated. The brilliant colours of the gold and silver and violet Carp are well known. Many fishes are striped and spotted, or burnished with colours which almost lival those of gaudy birds, and it would be difficult to name a tint which coidd not be niatched among some representatives of the fish class. Too little, ho-.vever, is known of the habits and ways of life of these highly-coloured fishes to enable us to judge how far they are an advantage to the species which are thus characterised. STRUVTUKE OF flSllK^ In the matter of mental endowment fishes are probalil}- but little, if at all, inferior to the majority of the so-called higher animals. The angler knows well their caution, discrimination, cunning, and boldness, and how often his own powers and patience are exerted in vain in entrapping a tish who has grown wise as well as old in observation of the phenomena of the liver in which he lives. Fishes would appear to be capable of aifection, since Shai-ks, at least, frequently swim in pairs. Some genera are capable of being trained, and a few are known to be gifted with vocal organs which, to judge from the analogy of higher animals, may fairly be regarded as a means for the inter-communication or expression of emotions and experiences. Removed as fishes are from the conditions of daily observation by living in water, fewer observations have necessarily been made upon their intellectual characteristics than is the case with animals which can be more easily studied. In their genei-al structure or anatomy fishes are usually well distinguished from other animals. 'I'heir most distinctive structures are, perhaps, the possession of gills and an air-bladder. But they are no less well defined by the j)cculiar forms assumed by the limbs which we call fins, and by the sinijilicity of the plan upon which the immense muscles, which form the larger part of the fish's body, are arranged. The variety in structui'e, how- ever, presented by fishes is so great that the lowest type — represented by the Lancelet — seems almost to pass beyond the limits of the tish gi'oup, standing alone in its simplicity and in many details of structure in which a parallel can be traced with yet lower animals. Other fishes also diverge so far from the typical forms as to lungs, as may be seen in the Ceratodus of the Australian rivers, and in the Mud-fish, called Lepidosiren. It may be useful briefly to mention the chief characteristics of the sevei-al groups of organs of this class of animals. In the lowest type of fish, of which the Lancelet (Amphioxus lanceolatus) is the only repre- sentative, the cranium is merely a foi-ward continuation of the rod which represents the vertebral column. This rod is named the notochord, or chorda dorsalis, and consists of a fibro-gelatinous substance, which is not covered with cartilage or with bony matter. This gives a very imperfect conception .of the skull as usually seen in fishes ; yet a jointed cartilaginous arch extends downward round the region of the mouth, and is a foreshadowing of the arch which is more perfectly developed around the mouth in the Lampreys. In simplicity of skull-structure the Sharks and Rays are the next step in the upward serie.s, but there are many points in connection with these animals which lead to the belief that they are among the highest types of fish. The notochord is now converted into firm granular cartilage, sheathed in bone, and divided into segments by bone de- posited in its sub.stance ; but it extends forwai'd along the base of the skull, and develops two oblong convex surfaces, which are termed the occipital condyles, by which the back of the skull unites with the first vertebra. This mode of union of the skull with the vertebral column is characteristic of amphibians and mammals, and since the other Vertebrates have the skull united to the vertebral column by a single occipital condyle^ it has sometimes been thought that we may discern herein a special indication of affinity between the skulls of Sharks and those of the Amphibia, which, it will be remembered, possess, when they commence their existence, many of the structures of fishes. There is no distinction of bones, however, in the brain-case, but the bony matter is deposited in countless little cells. Its base is flat ; the sides are contracted ; it is usually flattened above, with one or more open spaces, or fontenelks, which are covered only SKELETON OF THE COMMON PERCH. I. Pre-raaxIUary Bone; b, Maxill.iry Pniie: c Under Jaw: d, Palatine Arch: e. Cranium: operculum -.nil'. Vertebral Column ; Ii, Pectoi-al Fin ; i. Ventral Pin ; k, I. Dorsal Fins ; in, A with ■X NATURAL HISTORY. membrane. Indeed, this bony structure cannot truly be called a brain-case, since it is merely a covering on the outside of the cartilage which contains the brain. The arches appended to this cranium are a single strong pedicle on each side, wliich is articulated to an angular posterior process, and has attached to it the arch which is called the mandible, or lower jaw, and the arch which is considered to correspond to the tongue-bone in reptiles and birds, and is hence called the hyoid. The maxillary arch, or upper jaw, is closely joined to its fellow in front by a ligament, and is attached by ligaments to the anterior part of the cranial region, and is prolonged backward so as to articulate with the lower jaw. Each lateral half of the jaw consists of a single cartilage, or cartihige sheathed in bone, and thus far is comparable only with the jaws in mammals. According to Sir R. Owen, there aie also cartilages which represent the palatine and pterygoid bones in the Monk-tish and in a Brazilian Torpedo. Four or live cartilaginous rays diverge from the hinder margin of the pedicle which supports the jaws, and have stretched upon them a membrane which corresponds to the operculum in bony fishes. The hyoid arch in the Shai'k family usually consists. of two long and strong lateral pieces, which are united to a middle symmetrical piece below, wliich is flattened, termed the basi-hyoid. The two lateral portions, which rise from this like horns, and are hence termed the cerato-hyoids, give off .short cartilaginous processes from their hinder margins, which correspond to the bones which are termed branchiostegal rays in bony fishes, and support the outer membrane of the sac which contains the gills. The five branchial arches which extend backward behind the hyoid arch are suspended from the sides of the front vertebrie of tlie trunk, just as in the Lamprey. In Sharks three strong cartilages are prolonged forward from the head^ which coalesce in the middle line and form the remarkable snout. In these fishes the shoulder girdle is suspended a little behind the head. The ear is contained in a cartilaginous capsule in the walls of the cranium, the eye is united by a cartilaginous pedicle with the orbit, and the nasal sacs are arched over by nasal processes from the skull. Another modification of skull is seen in the Lepidosiren, where the separate bones of the skull are distinctly formed. The fibrous sheath of the notochord is ossified at the anterior end, and the ex-occipital bones rise from it, and expand and converge so as to meet above the foramen magnum. A large cartilaginous capsule surrounds the intej'nal ear, but there is a long basi-cranial bone with cartilaginous plates at the sides. Other bones of the upper part of the skull also have representatives. Each branch of the lower jaw consists now of two piece.s — the hinder portion, termed the articular, and the anterior, termed the dentary, though the two dentary pieces have become united together in the middle line in front. There are some slight representatives of the opercular arch. There is a single cerato-hyoid bone on each side, but no basi-hyoid. In one of his lectures Sir R. Owen remarked of this fish : — " I believe • it to manifest, upon the whole, the highest grade which is attained in the class of fishes, or in the direct progress to perfection in what may be termed the vertebrate high road. The true or typical osseous fishes deviate from this road into bypaths of their own, and superadd endless com- plexities, of which we shall seek in vain for homologous parts in reptiles, birds, or mammals. The Lepidosiren's skeleton presents the closest resemblance to that of the lowest class of reptiles, though it differs therefrom both by a little less and a little more development." The skull in osseous fishes is altogether different. It may be' convenient, as the modifications which it presents are so multi- tudinous, to bear in mind as one type the skull of the Codfish {Gadus morrhtut), which is one of the largest and commonest British specie.s. The head is larger in proportion to the trunk in fishes than in any other class of animals. It is more or less conical. The base of the cone joins the trunk without any intervening neck ; the jaws are usually at the apex of the cone, which is flattened above, and has the sides more or less converging below. The eyes are large, and the orbits communicate with each other. There are two lateral fissures behind the head, which are called the gill-apertures, and are opened and closed by special mechanism. Besides receiving the food, the mouth takes in streams of water for respiration, which, after bathing the gills, escape by the gill-apertures or openings behind the operculum. The head also contains the heart and the whole of the breathing organs, and the anterior limbs are often in very close union with the skull. There are more bones in the head of a fish than in the head of any other animal. Most of these bones unite with each other by overlapping, like scales. The brain is contained in a cranial cavity, so that the bones fit closely upon it. The upper surface of the head is often marked by longitudinal crests, but sritUCTUllE OF 1-lsUES. it does not often happen tliat the temporal muscles, which work the lower jaw, extern! to the upper surface of the cranium, though this sometimes occurs, as in the Conger Eel and in the Lepidosiren. Tiie bones of tlie skullras in man, are divided into those of the brain-case and those of the fiice; but in fishes the facial bones are far more developed than in man. The liindermost bone at the back of the skull, by which it joins the lirsfc vertebra, varies a good deal in form. In most fishes, as in the Carp, it is a deep conical cup, but in the Holibut it is almost flat, and in Fistularia it presents a convex surface, which is exactly comj)arable with the condition seen in a Lizard or Crocodile. This bone, which is termed the liasi-occijjital, in many fishes has a jirocess prolonged downward from its under side, and in the Carp this broad triangular plate supports the large upper gi-inding-tooth in the throat, reminding one of the way in which processes from the neck vertebrre are prolonged into tlie oesophagus in certain Snakes and Lizards. There are two bones rising from the basi-occipital which arch over the beginning of the brain ; they are termed the ex-occipitals. They are usually perforated for the pueumo-gastric ner\e, and sometimes for other nerves also. The bone above these is called the supra-occipital. In the Cod it is prolonged back- ward in a median spine ; iji the bony Pike (LepiJosteus) it is double, being divided by a suture in the middle line. Sometimes the crest of the bone is e.Kceedingly lofty, as in the Light Hor.seman fish {Eph'ippiis). and sometimes absent, as in the sucking fish Remoiva. At the sides of the ex-occipitals are two bones, termed by Owen par-occipitals, and by Huxley opisthotic bones. The distinction of these bones in the lower Vertebrates is a characteristic feature of the skull, but in the Polypterus they unite with the ex-occipital bones, as in Batrachian reptiles, and in the Chad they unite with the mastoid bones, as in the Chelonia. The organ of hearing in fishes is usually large. In front of this girdle of cranial bones, ■which Sir R. Owen long ago com- pared to one of the trunk ver- tebra, is a similar series of bones with a median basal bone, now called the j^^i'^^-sphenoid, and closely resembling the para- sphenoid of Amphibians, which reaches along the greater part of the base of the skull, exactly as in that group. In the flat fishes its anterior end is twisted upon one side of the skull. It is always smooth below, and in the genus Polypterus the bones which rise fi'om its sides are blended with it. There is some difference of opinion with regard to the names to be given to these bones. The liindermost bone is termed by Owen ali-sphenoid, and by Huxley prootic. These bones are arched over by the parietals. In the Salmon family the two parietals soon unite together. In the Siluroid fishes they also unite with the supra- occipital bone, but in many osseous fishes the supra-occipital bone extends between them. They are always flattened above. In some fishes they are perforated by nerves which supply the vertical fins of the back. In front of the ])arietal bodes is the principal frontal, which roofs over the orbits in all animals. It carries a median crest in the Cod and some fishes, and varies in .shape ■i\ath the form of the skull. In the Tunny each frontal has a crest of its own, and in some Siluroid fishes and the Loach there is a fontenelle between the frontal and parietal bones which corre.sponds in position with the ao-caXled. foramen parietnle, which is characteristic of many fossil and living reptiles. In the flat fishes the frontal is single. Behind it at the sides are the post-frontal bones, which assist in arching over the auditory cavities, and help to furni.sh a support for pjii SKULL or CDnrisH {Ga.his mori-IiiM). [,Aftcf Orceii.] Nasal; /.Frontal: s, Supia^icripital i pm, Prc-ma-tillarj; ra. Maiil ni; j».o., Siili-operculum; o. Opercnluin; p.o.. PlT-operculum: ft.m.. Hyo-nm %., Cerato-byal; &. Bi-aucbiostegal Rays; ps, Para-sphi-uoid ; d, Deutary. 6 X AT V It A I niHTOET. the tympanic pedicle. At their anterior corners are tlie pre-frontal bones, which defend and support the olfactory prolongation of the brain, and form the front border of the orbit. On the base of the skull, wedged into the para-sphenoid, is the vomer; its upper surface supports the nasal bones. In the genus Lepidosteus it is divided longitudinally into two. In many fishes the vomer carries teeth. The prefrontals and nasals are both sometimes blended with the vomer. The nasal bone is broad in the Salmon, but varies in shape in other fishes. In the genus Lopliius and in the Diodonts it is unossified, being represented by membrane. The nasal bone completely divides the nasal cavity into two lateral pits. Between the orbits there is often a partition, which is sometimes cartilaginous and sometimes membranous. The turbinal bones of man, on which the olfactory nerve is spread out, are represented in the fish, and placed at the sides of the nasal bones. The nasal bone sometimes supports teeth, and teeth are frequently found on the palatine bones. The sense capsules are well fitted into cavities of the skull in bony fishes. The auditory organ becomes blended with the cartilaginous base of the skull in Lepidosiren, and there ai"e distinct otic bones, which protect the labyrinth of the ear in many bony fishes. These auditory capsules are often closed externally, but have a wide opening into the cranial cavity. The eye in cartilaginous fishes is contained in a cartilaginous capsule, but in most osseous fishes the capsule is bony. Bony plates are developed in some fishes in the sclerotic or hard outermost covering of the eye. In most fishes the bony orbits for the eyes communicate with each other, but the Shads, Hydrocyon, Synbranchus, Cyprinus, and many other genera have a bony septum between the orbits, and in the Ganoid fishes of the genera Lepidosteus and Polypterus the orbits are divided, as among the Batrachia, by a double septum, which forms the walls of the olfactory prolongation of the bi-ain. The bones which form the jaws may conveniently be considered together. They are somewhat diffei-ently arranged in fishes to their condition in other animals, but the bones are still easily identified by the same names ; thus pterygoid, palatine, maxillary, and pre-maxillary still mark the order of succession of the bones of the palate from behind forward. The palatine bones unite in front with the maxillary, pre-frontal bone, and vomer, though in some fishes certain of the attachments are made by ligaments. The palatine usually forms the roof of the mouth as well as the floor of the orbit, and is always short and broad in the fishes with broad heads and small mouths, and long and slender in the fishes with wide mouths. The presence or absence of teeth on the palatine bone furnishes an excellent character for distinguishing many genera. The maxillary bone is usually small and toothless, and lies between the palatine bone behind and the pre-maxUlary in front. In shape it is usually like the pre-maxillary, but more slender. In the Salmon tribe it unites with the hinder end of the pre-maxillary, which is short, and carries teeth along its mai-gin. This condition also occurs in the Herring family, while in the Plectognathi, or Globe-fishes, the maxillary and pre-maxillary are blended into one bone. In the genus Lepidosteus the.se bones, although forming a single toothed border to the upper jaw, are subdivided into several bony pieces, but in the genus Polypterus the maxillary shows no signs of subdivision. This bone is very small in the Siluroid fishes, and both it and the pre-maxillary are entirely wanting in some of the Eels. The pre-maxillary bones are usually movably connected together at their anterior ends, but in the genus Diodon they are completely blended. The blended pre-maxillaries form the sword-like weapon in front of the snout carried by the Sword-fi.sh (Xipkias) and by the Gar-pike. The pterygoid and transverse bones are not always present, though they occur in the majority of fishes. In the Salmon tribe and Eels they are blended with the palatine, and in some other fishes, like the genera Lophius and Synodon, they are entirely absent. Both these bones some- times support teeth. The mandible, or lower jaw, is sometimes united in the median line in front by bony union, but sometimes the union is made by ligament. In front there is a bone which carries the teeth, called the dentary bone. This usually contains within it a cartilage, which is known as Meckel's cartilage, and the other bones placed behind the dentary ai-e arranged ai-ound this cartilage. The lower jaw, however, joins the skull in osseous fishes in a way that is quite unpai-alleled among other animals. There is a distinct arch foi-med by a series of bones, which supports both the mandible and the gill-cover, and this arch is jirolonged up the sides of the head, so as to imite with its side in the auditory region. The mandibular arch, however, is not altogether distinct from another arch placed behind it, which is termed the hyoid arch, and corresponds with the bones which in higher animals are connected with the tongue. The several portions of the hyoid have received STEl'vrUME OF FISHES. 7 distinct niiines : first there is tlio basi-liyal in the middle, and from this a bone termed the glosso-hyal usually extends into the substance of the tongue. At the sides rise uj) the long horn-like bones termed cerato-hyal, aljove this is the epi-hyal, and yet higher still the stylo-hyal. All these tracts arc not universally met with. In the Conger Eel, for instance, stylo-hyal is a ligament, and the basi-liyal is blended with the cerato-hyal. In other fishes, like the genus Mursenopliis, the glosso-hyal is wanting. From the hinder margin of the cerato-hyal and epi-hyal a number of slender, long, curved bones are prolonged backward and outward. These are termed the branchiostegal rays. They support the membrane which forms the external cover to the chamber which contains the gills. Their number is very variable, but most usually seven, as in the Cod. In the Herrings of the genus Elops there are more than thirty rays in each gill-cover. In the Carp they are fiat and broad, and reduced to three in number. In the Angler they are enormously long. Behind the hyoid arch, and more or less connected with it, are the branchial arches. Originally there were six of these arches, one behind the other, with clefts between them, but only five are commonly developed. The first four support the gills, the fifth, margined with teeth, guards the entrance to the gullet. The lower ends of these arches are united to a chain of little bones prolonged backward from the basi-hyal element of the hyoid. This part, usually termed basi-branchial, most frequently consists of three bones. Each branchial arch rises from this outward and upward. It consists of three or four separate pieces of bone, though the fifth arch commonly consists of one bone only. Sometimes these arches become complicated in fishes which live long out of water, such as the Climbing Perch, by developing at their upper margins large bony folds, in the recesses of which water is contained, so that it may trickle from them over the gills. Occasionally the branchial arches remain cai-tilaginous, and all six pairs retain the cartilaginous condition in Lepidosiren, but the second and third arches do not sujjport gills, though they are found on the last arch. The scapular- arch of the fish is often attached to the side of the skidl, or occasionally to the basi-occipital, though in the cartilaginous fishes it is usually removed farther back. It consists of several bones, which have received different names from the several anatomists who have described them. In Sir R. Owen's system the uppermost piece is the supra-sca|)ula, which sometimes consists of two short columnar bones attached to the auditory region of the skull. The next piece is termed the scapula, and these two bones are always blended together in the Siluroid fishes. The lower bone Sir R. Owen terms the coracoid. They are sometimes blended together at their lower margins, but more frequently these bones are joined by ligament, though in the Siluroids they unite by a toothed suture. The bones which Owen names scapula and supra-scapula Huxley, with good reason, calls clavicle and supra-clavicle. The scapula and coracoid in all animals form the aj'ch which gives attachment to the base of the limb. These bones support and defend the heart in all fishes, and give attachment to the diaphragm which separates the cardiac cavity from the abdominal cavity. They also furnish a margin against which the operculum shuts, enclosing the cavity which contains the gills. The vertebrje in fislies present many curious modifications. Thus, in the Sturgeon the first five or six neural arches are blended together so as to form a sheath of cartilage which encloses the spinal cord and the front ]iart of the notochord, the tapering end of which is prolonged into the base of the skull. The ribs are attached only to about the first twelve of the trunk vertebrse. They join the vertebrse by simple heads, and often consist of two or three jointed pieces. The .same kind of union of the earlier dorsal vertebrse into a continuous cartilaginous sheath around the notochord is formed by the first ten vertebrse of the Chimaaroids. In some of the Sharks the ribs become very numerous, extending in Acanthias to forty pairs. Among the Skates of tfie genus Rhinobatie, Sir R. Owen finds but a single arch over the bodies of two vertebne, and in the Chimaera the slender rings which represent the bodies of the vertebra? in the cartilage covering the notochord are more numerous than the neural arches which extend over them. In the Blue Sharks the vertebra? are most perfectly ossified, having only four notches for the neural arch and transverse processes. In most bony fishes the vertebrse are conically cupped at both ends ; often the body of the vertebi-a remains distinct from the neural arch. In most animals the front of a vertebra is easily recog- nised by the processes called zygapophyses, which yoke the bones together in front and behind, the articular surfaces in front always being directed upward or inward, but in the Perch the reverse condi- tion is met with. The posterior zygapophysis here looks upward, and receives upon its surface the y NATURAL HlSroKY. overlapping anterior process of the next succeeding vertebra. The transverse processes are short in the Salmon and Herring, but very long in the Cod fondly. As these transverse processes approach the tail they bend down and form a canal which arches over the blood-vessels in exactly the same way as the neural arch protects the spinal cord. The ribs of fishes sometimes articulate with the ends of the transverse processes, occasionally beneath them, and sometimes behind them, but the rilis are not uixiteJ to a sternum, as is the case in the liigher Vertebrata. A considerable numuer of fishes, such as Globe-fish, Sun-fish, and Pipe-fi.sh have no traces of ribs. The most siiigiilar example of vertebriB becoming blended together is seen in the neck of the Pipe-fish {Fislu- lariu), in which four neck vertebrie are united into a mass like the sacrum in birds. A true sacrum, however, occasionally exists, as in the Turbot, -where two vertebra are blended together, and in other fishes, like the genus Loricaria, a longer sacrum is developed. The number oi vei-tel>i-£e in osseous fishes is smaller than in the cartilaginous fishes. In the genus Gymnotus, however, there are 236, but in the Sun-fish Sir R. Owen enumerates only eight alidominal vertebrie, and eight in the tail. In the American bony Pike the vertebrae have the bodies convex in front and concave behind, but no fish is known in which the reverse condition of the cup in front and ball behind is met with. Often in fossil fishes the bodies of the vertebra are unossified, while the neural arches are well developed. Then the notochord is said to be persistent, and occasionally it is sheathed in rings of bone. The muscles of fishes are arranged on each side of the body in a series of successive flakes, which correspond in number witli the vertebra. Each of these flakes is attached by its inner border to the corresponding region of the skeleton and by its outer border to the skin. Each muscle or flake is contained in a sheath of connective tissue, which dissolves when the fish is boiled, so that the flakes then readily separate. The fibres of each muscle-flake run straight and nearly horizontally from one partition to the next, so that they extend longitudinally in the length of the fish. In the tail especially these muscles overlap each other, so as to present the same conical form at their ends as is seen in the tails of Crocodiles and Lizards. There are longitudinal divisions of the muscles in most osseous fishes which correspond more or less closely with those observed iir the fiiih- like Batrachia and Ophidia. Towards the head these muscles become specially modified. Both the jaws in fishes are movable as a rule ; and the large square muscle which draws the mandible back- ward stretches from the tympanic region to the maxillary bone, and by another branch to the coronoid 2)rocess of the lower jaw. This mu.scle tends to open the fish's mouth. Other muscles widen the back of the mouth, and contract the bi-anchial cavity. There is a series of muscles attached to the hyoid apparatus and the opercular bones by which the requisite muscular movements necessary to respiration are brought about. The branchial arches are similarly supplied with muscles. The muscles of the pectoral fin are arranged in two layers on each side ; the fibres run in opposite directions, so as to cross each othei-. The inner pair retracts the fin, drawing it back so as to touch the side of the body. The outer pair extends the fin or moves it in the ojiposite direction. Then there are special muscles for depressing and raising the fin. Similar muscles control the ventral fins. Muscular fibres act upon the rays, and there are nuiscles to expand the rays and move the fins in the various directions which they are capable of taking. The median fins have three or four pairs of small muscles attached to each ray, and by these the rays are elevated and depressed. The caudal fin is moved by three series of muscles, but the variations in the muscular system of fishes are extremely numerous. The sucker of the mouth of the Lamjn-ey is worked partly by a circular muscle, termed a sphincter, like that which closes the mouth or the eye in man, and ])artlv by a series of muscles connected with the hyoid cartilage and with the lateral muscles of the body. The Trunk-fish, which is sheathed in bone, and is therefore incapable of lateral movement, has the longitudinal muscles of the body rediiced to a thin layer. The muscles attain their gi"eate.st develo]>ment among the Sharks. In fishes tlie substance of the muscle is usually colourless, owing to the small quantity of blood which it contams ; but in some Sharks and the Sturgeon the muscles of the pectoral fins and the caudal extremity are deeply coloured, and nearly all the muscles of the Tunny are red, like those of mammals. The orange-i-ed colour of the flesh in the Salmon and Charr is not due so much to the colour of the blood as to a peculiar oil which exists in the sheaths of the muscular fibres. The skin is tightly ■ stretched over the body in fishes, and enjoys but little sensibility, through being, for the most part, clothed with scales. In the Lamprey the skin consists of two layers, with STECCTl-RE OF FISHES. 0 flattened fibres running at right angles to eacli otlier; the outer hxyer, or ei)i(lermis, is full of large star-shaped pigment cells, but devoid of scales. The Eel has a soft and thick epidermis. Below the pigment layer are the narrow oblong scales, which are formed of a finely reticulate cartilage. In the genus of Blennies named Zoarces there are circiilar depressions over the skin, due to minute round scales embedded in tlie dermis. Most osseous fishes possess flexible scales, marked with either con- centric or radiating lines, or both combined. In these scales there is usuallj- a nucleus, wliich may be irregular. The radiating lines diverge from the circumference of this nucleus. These lines are very numerous in the scales of the Loach (Cobitis). Tlie parts of tlie margin of the scale l)etween the radiating lines usually pi-oject in little con^-exities, and when the irregularities are limited to one end of the scale that end of the scale is usually implanted in the skin. In many tishes the free end of the scale is bordered with tooth-like processes. The surface of the body in most fishes is lubricated with a thin layer of mucus, but in the Eel and Tench the mucous layer is thick. This fluid is secreted l>y a canal which extends along the body, and has many ramifications among the bones of the head, where it exudes through pores upon the cranium, face, jaw.s, pre-operculum, and through tubes which 2)ei'forate the scales along what is called the lateral line, usually distingui.shed on the sides of the tish by a lighter or darker colour. Rymer Jones remarks that after a fish has been dried in a napkin it soon become^. f^^^ r^?^^5^ covered again with mucus, which issue.s from the pores. In the Tuni \ {ThynmiJS l/ii/nnus), there may be seen beneath the skin, running tl entire length of the lateral line, a glandular organ, from which the litti tubes are given off to the lateral line. The mucous system, howe^ei, is best developed m the Rays. In the genus Acanthoclinus there aie se^ ei U lateral catials which give ofi;" -short tubes, which tunnel a way through the scales as they pass onward. Sir Rich Owen remarks that the silvery and golden lustre of fishes is mostly on the surface of the scales The silvery pigment known in commerce under the name of aigentine ^ ali- . i consists of very minute crystals of various earthy substances sciaped » I'lit'ni from the scales, which often also occur upon some of the internal organs. The blue, red, green, and other bright colour.s of fislies are usually due to coloured oils, which occupy cavities in the skin, and are capable of changing their position, so as to alter the colour of the fish under the influence of excitement, or in harmony with the colour of the sea- bed upon which the fish is living. Many fishes change colour after death. The scales of fishes consist of two layers. The lower layer resembles the fibro-cartilagn of the human body, while the upper layer contains cartilage cells similar to those which are seen in the bluish cartilage covering a joint. The parts of a scale are defined in relation to the nucleus or focus from which gro\\i;h originates. The longitudinal lines which run out from this nucleus some- times form furrows and sometimes perfectly closed tubes. The broad plates which form the armour of the Pipe-fish are penetrated by canals, which all converge from the margins towards the middle of the scale. The concentric lines of scales are found to originate in the development of new cell^, which become filled with horny matter, and ultimately arrange themselves in concentric lines. Scales show, when examined with the microscope, corpuscles, which are similar to those seen in bone. The fibrous layer of the scale may easily be found by scraping off the external cellular lines and corpuscles, when the fibres of the lower layer will be seen to cross each other at various angles. The growth of the spines upon scales appears to be similar to the growth of teeth, for each spine is contained in a distinct capsule or envelope. When the capsule is opened the spine can be easily removed from it, but as the germ develops it acquires roots, and comes to consist of several layers. Professor Agassiz, impressed with the differences of form m the scales, at one time believed that fishes might be classified by means of them, and he proposed to divide the scales into four types : those which were bony, and formed of a thick osseous layer, covered with hard transparent enamel, as in the genera LepidosteuR and Polypterus, were termed Ganoids ; those dermal spines or tubercles seen in the Thornback and many other cartilaginous fishes, which have a spine arising from a more or less cii-cular bony base, were called Placoid scales ; the scales which have the free margin more or less comb-shai>ed were termed Ctenoid ; and those marked with a concentric structure were named Cycloid. NATURAL HISTORY. To the two latter grovips the great multitude of living fishes belong, but in the earlier ages of the earth's history Ganoid fishes were the prevailing ty[)es. Hence the older and less peifectly ossi- fied division of fishes has been named by Dr. Giinther, Palseichthyes. The nervous system in fishes presents an unusual amount of variation. In the Skates there is a slight enlargement of the spinal column in the region where the large nerves are given oflf to the pectoral fins, and the same condition may be noticed in a less degree in the Sharks, but no corresponding enlarge- ment of the spinal cord has been noticed iu the Flying-fish or any other osseous fishes. In the Sturgeon there is a slight enlargement of the spinal cord at the beginning of the caudal region ; in the Sun-fisli the spinal cord is said to be reduced to a short conical appendage to the brain ; and in the genera Tetrodon and Diodon the spinal cord is exceedingly short and small, but it has not the ganglionic structure seen in the Sun-fish. But in most fishes the spinal cord is as long as the neural canal. It i.s often marked by longitudinal fissures along the ventral and dorsal surfaces ; and in the Sturgeon there is a less complete lateral groove dividing the spinal cord into dorsal and ventral columns. And in many fishes, such as the Cod and Herring, six cords may be distinguished : two of which are dor.sal, and govern sensation ; two ventral, and govern motion ; and there are also two lateral regions. As the spinal cord approaches the brain it enlarges. According to Sir Rich. Owen, fishes are especially disting\iished by having lobes which correspond to the great vagus nerve, or pneumogastric, as it is usually called, extending into the fourth ventricle of the brain, which is a cavity at the beginning of the medulla oblongata, or part where the brain becomes connected with the spinal cord. The brain has its parts always arranged one behind the other in longitudinal .succession, as among Amphibia and Reptiles. There is a hiiidermost part, which is single, called the cerebellum, which in most fishes is comparatively small, but becomes large and marked with transverse folds in the Sharks and Rays. Placed in front of this are two more or less I'ounded or ovate masses of brain, called the optic lobes. Farther still in front is the cerebrum, which usually consists of two masses, which may be larger or smaller than the optic lobes ; but among the Sharks and Skates these masses of the brain are usually more or less blended together. In many fishes there are, besides, large olfactory lobes placed in front of the cerebrum, and from these the nerves of smell are prolonged. The nerves are in other animals, and the spinal cord prolonged down the vertebral column gives off nerves usually from between the vei'tebrie, though occasionally, as among some Sharks, they pass through perforations in the bony arches which cover the spinal cord. In most osseous fishes the cerebellum is smooth and convex ; it is frequently hemispherical, as in Amblyopsis, a genus of blind fish. In the Eel it is transversely elliptical ; in Lepidosteus it is longi- tudinally elliptical ; it is oblong in the genus Diodon ; it is a depressed tongue-shaped body in the Cod ; it is pyramidal in the Perch, and attains an immense development in the Sharks, where it extends 'over the optic lobes, which is also the case in the genus Amblyopsis ; while in the Saw-fish it extends forward so far as to rest upon the cerebrum. It is largest in the most active fishes, is very small in the Lump-fish, is unsymmetrical in some of the flat fish, has a longitudinal groove in the genus Diodon, Mid is transversely divided in the genus Lophius. The fishes in which it shows the branching interior structure called the " arbor vitje," due to the grey matter being folded over the white nervous matter, are Sharks and the Tunny. Another peculiarity of the Skate tribe, and found in most of the allied fishes, is the development of large convoluted lobes at the sides of the medulla oblongata, in the position where the fifth nerve is given off, a condition well seen in the Torpedo and in the Chimcera monstrosa. ITie optic lobes are usually the lai-gest portion of the fish brain; they are spheroidal. Prolonged downward from this region is that remarkable part of the brain called the pituitary body, and upward the pineal gland is given off in front. There is a cavity in the optic lobes, which is one of the ventricles. It is quite exceptional for the optic lobes to be smaller given off from the brain, precisely STllVrrVliE OF FISHES. U tlian the cerebral lobes of the brain, as they are in the genera Polypterus and Lepiilosiren. In the Blind Fish (Ambli/opnits) the optic lobes are exceedingly small. In several fishes, such as the Sturgeon, the optic lobes are almost completely united into one mass, but even where they are most widely separated, as in the Perch and the Herring, they are connected by a transverse band which passes in front of the third ventricle. The cerebral hemispheres often have a pinkish appearance, and the nervous matter is fissured and sometimes nodulated, but never approaches the convolute character seen in the higher mammals. These nervous masses are large, smooth, and elongated in many fishes, and in the Sharks become blended together ; but in the bony fishes the cerebrum is proportionately small, especially in the Herring. It is also small in the Perch and Bream, but is relatively largest in the Ganoid fishes, which have hemispheres exceptionally large. The cerebral lobes are usually solid, but sometimes contain a lateral ventricle. The olfactory lobes are two distinct masses of grey nervous matter, which are never linited by a transverse band, and may be in contact with each other in front of the cerebrum or widely separated. The true olfactory nerve consists of a group of distinct fibres, where it is given off from the olfactory lobe of the brain. The cerebi-al hemispheres of fishes coiTespond to that portion of the brain in mammals known as the corpora striata. The relative size of the brain to the body may be gathered from the fact that in a Carp weighing 11,280 gi-ains the brain weighed fourteen grains. As witli higher animals, the brain acquires its full size before the fish has attained its full gi-owth, and hence is relatively smaller in old fishes than m young ones. The great develojjment of the medulla oblongata in fishes has a direct relation to the large size of the respiratoi-y organs, or gills. The development of the cerebellum, so remarkably seen iia the Sharks and Rays, is connected with active locomotion. Sir Rich. Owen observes that there is a distinct relation between the form of the brain and the habits of the fish, but all fishes of the same habit have not the same types of brain. " Thus the Shark and Pike are ferocious and predatory, the Angler and Skate are crafty, the Sword-fish and Stickleback love fighting, and the Barbel and Carp are timid, peaceful browsers. If the cerebral hemispheres of the Shark and Pike are compared, these parts of the brain difier more in shape, size, and structure than in any other fishes, though they are equally sangumary, equally insatiable, both unsociable, and are tj'rants, one of the sea and the other of the lake. The cerebrum of the Pike is smaller than the cerebellum ; in the Shark it is larger than all the rest of the brain. In the Pike the two lobes are distinct, and united only by a narrow transverse band, but in the Shark they are blended into one large globular mass. In the Pike the cerebral lobes are narrow, but in the Carp it feeds upon they are broad, and in the fighting Stickleback the cerebral hemispheres are longer and naiTOwer than in the cowardly Gudgeon." The organ of smell in fishes has no connection with the mouth, and is in no way connected with respiration, as in higher animals. In the Lamprey and Hag {Myxine) it is single, but in all other fishes there are two olfactory organs. In osseous fishes these organs are placed at the sides of the snout. The Wrasses have a smgle opening for each nose sac, but in many fishes there are two, and then the anterior one is closed by a valve or circular muscle, and the posterior one is open. In the Sharks and Skates the nasal cavities are on the under side of the snout, and here the single wide opening is defended by a valve. The organs of sight in fishes are marked by a few peculiarities ; thus, there is no lachrymal gland, the eyes apparently being sufiiciently moistened by contact with the water. In the Hag and some other fishes the eye is a mere speck coated with dark pigment, but, as a rule, in osseous fishes the eyes are large, and are especially conspicuous in the Sun-fish. The crystalline lens is large and firm ; the fibres which fomi it usually converge to two poles, like the meridians on a globe, but in the Salmon tribe and Sharks they converge to a line on each side. It was found by Sir David Brewster that the fibres of the crystalline lens in the Cod are locked together by teeth, like those on cog wheels. He calculated that in the eyes of a Cod there are five millions of fibres, on which there are sixty-two thousand five hundred millions of these teeth, and yet in the living animal the organ is perfectly transparent. The pupil of the eye is usually round, but in many Sharks it is elliptical, and in the genus Galeus it is four-sided. In the Skates and flat fish a remarkable fringed process is connected with the upper margin of the pupU, and is capable of being let down and drawn up like a curtain, to regulate the quantity of light admitted to the eye. This would seem an arrangement to supplement the feeble contraction of the iris in fishes. In the Sharks and Sun-fish the eye is contained NATURAL ML'iTuRY. in a liollow cartilaginous slieatli, but usually the slieatli is foruied of two hemispherical cups, which are souietiines cartilaginous and sometimes bony. There is often a good deal of fat bttween the outer sclerotic layer and the more vital internal parts of the eye. In the fresh-water genus Anableps the cornea is divided by an oi)aque horizontal line, on each side of which the iris is perforated bv a pujiil. The muscles which move the eyes of tishes correspond with those of man, and are usually six in inimber. The organ of hearing is well developed in all fishes ; the membranous labyrinth in the Lamprey has only two semicircular canals, and in the Myxine there is only one of these canals, but in all other fishes there are three, as in higlier animals; they communicate with a vestibule, in which are contained the bony plates called otolites; there are usually two of these flattened, somewhat oval organs, and one is larger than the otiier. But in a good many fishes, such as the Plectoguathi and Lophobranchiates, the otolites are represented by calcareous dust. No fish possesses a cochlea or a true tympanic membrane, but sometimes there is a connection between the labyrinth of the ear and the air-bladder, made by a chain of small bones. In the Loach the air-bladder is exceedinglj' small, extending under onlj' two vertebra;, and is united with the head in this way. The external ears in the Skate are on the top of the head. Closely allied to the organs of sense must be classed the electric organs of fishes, though the electric faculty is developed in very few genera. The best known of these are the Torpedo and the Electric Eel (Gymnotus), though less powerful electric organs exist in various s}iecies of Malapterurus, and are said to exist in Tricliiurus, Gymnarchus, and a species of Tetrodon. In the Torpedo there are two electric organs; in the Electric Gymnotus there are two on each side of the body, where they occupy almost the whole of the lower half of the trunk, and are arranged on the upper and lower sides of the body. The electric organs are relatively larger in the Gymnotus, but their electric power is less. In the Malnpturtifus ekctricus the electric organ lies beneath the skin, and invests the whole body, with the exception of the head and lins. The electric organ is here divided into minute lozenge- shaped cells, .so that the fish is protected by an electric coat, but the shock from it is comparatively feeble. In the genus Mormyrus a gelatinous organ placed on each side of the tail was formerly believed to be electric. The teeth of fishes present, a remarkable variety in their forms and numbei-s. Sir Rich. Owen remarks that the Lophobrancliii ai'e toothless, as are the Sturgeon, the Paddle-fish, and Ammocetes, which is the larval form of the Lamprey, requiring four years for its development. The Myxine has a single-pointed tooth in the roof of the mouth, and two serrated dental plates upon the tongue. The Tench has one grinding-tooth on the occiput, opposed to which are two jaws in the pharynx below which bear teeth. In the genus Chimsera the teeth in the maxillary bones are confluent into two pairs, and there are two teeth in the mandible, but in the Siluroids and many other fishes the mouth is crowded with teeth. A large number of fishes have conical teeth; several of the Rays, like Mylio- bates, have the teeth arranged like a tesse- lated pavement. In the genus Citharinus the teeth bifurcate at their extremities; in the genus Platax they divide into three points. Sometimes there are hemispherical teeth an-anged like a pavement, as in the Wrasse. The rarest position for teeth in a fish is upon the maxillary bone, though they are developed there in Salmon and Heri-ings, and some Ganoids. In many fishes the teeth are blended with the jaw ; in Sharks their broad bases are usually attached by ligament ; in the remarkable snout of the Saw-fish organs like teeth are implanted in .sockets. Sometimes, as in the Wolf-fish (Anarrhichas), the front teeth are' adapted for .gi'asping shells, while the back teeth are fitted for crushing them. I}i all tishes the teeth are shed and rencM-ed many times during the FEMALE (b) skate. n-crritjE of fishes. whole duration of their lives ; the only teeth wliieli are retained permanently being those in the rostrum of Pristis, the dental masses of Chimtera, and a few others. The lips of lishes are not much developed ; in Sharks and Rays they are supported by cartilages. In the Cod there are fringed filaments between the lips and the teeth, and in several tishes there are tentacles attached to the lips, which assist in selecting food. There are no proper salivary glands in tishes, and the tonsils are entirely absent. The alimentary canal is usually short and large ; in the genus Lepidosiren it is almost straight. The front part, termed the oesophagus, is a funnel-shaped canal coated with a strong muscular substance, so that it grasps the food and passes it downward into the stomach. In many lishes the pneumatic duct from the air-bladder opens into the oesophagus, and in the Ganoid fishes the entrance to this canal is controlled by muscles. The stomach is usually a large simple cavity, with a capacious inlet and a small outlet. Sir R. Owen defines two kinds of stomach in tishes : first, the enlarged bent tube seen in the Cod, Salmon, Tench, Sturgeon, and most Sharks ; and secondly, the form seen in the Perch, Gurnards, Smelts, Pike, Herring Sprit, and Eel, iu wliidi the stomach forms a sort of j)ouch. It i', rare for the stomach to be globular, but this condition is seen in the genus Mormynis The stomach takes on some of the characteis of a gizzard, and in several fishes this oigan is more or less divided into two or thxee chambei-s. The juice secreted by this organ has a rapid action on food, and it sometimes hajipens that the part of an animal contained in the stomach is dissolved, while the pxrt which remained in the oesophagus is entiie Fishes disgorge the indigestible part of their food, and when caught frequently eject the animals they have swallowed. The intestine beyond the stomach is often short and simple Round its commencement in most osseous fishes thei-e are a number of slender pouches, which represent the sweetbread or pancreas of higher animals, but in the Lamprey and Hag there is no trace of a pancreas, and in a few tishes there is only a single filament to repie sent it; in the Turbot there are but two, and in the Perch three ; in the Sprat there ai e as many as nine, but in the Salmon they aie more numerous, and extend along the whole length of the first part of the small intestine, which is technically called the duodenum. In the Whiting this organ forms a fringe like a collar around the beginning of the intestine, and in the Sturgeon the pancreas becomes more compact, and pours its secre- tion into the intestine by a single wide duct. Sometimes the pancreas is heavier than the liver. The liver in fishes is generally large, and consists of two lobes ; it is soft, and usuall}' yellowish-brown, but varies in colour in different fishes, being sometimes white, yellow, orange, green, bright red, and occasionally nearly black. It is an organ in which much of the oil of the body becomes accumulated, though fat fishes have very little oil in the liver. The liver vaiies in foiui ^^ith the shape of the body, being broad in the Rays and long in the Eels. It is gi-eatly dn uled m the Tmmy. 14 XATURAL HISTORY. As a i-ule, there is a gall-bladder, but it is frequently absent ; it is very small in the Rays, and is sometimes entirely separated from the liver, as in Lophius. The bile enters the small intestine near the stomach. The internal surface of the small intestine is usually smooth, but in the Herring it shows slight transverse folds, in the Sturgeon it is divided up into cells, and in the Sun-fish it is lined with little tubes called villi, which absorb the nutriment from the food. The large intestine is straight, and in the Ganoid fishes. Mud-fishes, Sharks, and Rays terminates in a remarkable spiral coil. Though the small intestine is coiled up spirally in the Sword-fish, the coils are not in contact, but in the cartilaginous fishes there is usually a spiral channel which winds around many times. In the Fox Shark there are thirty-four of these turns ; at the end of the intestine the membrane lining the valve is deeply honey -combed. Evidence of its existence in fossil fishes is found in the spirally-formed coprolites or petrified fseces which are met with in many of the geological formations. The organs for purifying the blood, by separating from it the waste products, are difierent from the kidneys of higher animals, and correspond to organs which exist only in the embryo, and are known to anatomists as Wolflian bodies. Their function, however, is the same in fishes as that of kidneys in other animals. In most bony fishes the kidneys are long and narrow, and extend along the abdomen firmly attached to the vertebra. The tissue forming them is usually of a reddish tinge ; it is soft and spong}', and supplied with arteries from the abdominal aorta, which form the minute globular secreting organs termed Malpighian capsules, similar to those which abound in the outer layer of the kidney in liigher vertebrates. Sometimes two ureters lead from the kidney and enter a urinary bladder, but occasionally, as in the Hen-ing, there is only one uretei-, and in this and several other fishes the bladder is wanting. It is largest in those fishes in which the air-bladder does not exist. The kidneys are long and narrow in the Ganoid fishes, and compact and generally lobulated in the cartilaginous fishes. The air-bladder is found in most osseous fishes ; it extends along the back of the abdomen, below the kidneys, and is prolonged in some fishes below the caudal vertebrfe, nearly to the end of the tail. Its varieties of form are very singular: it is sometimes divided lengthwise into two bladdei-s, but much more frequently divided crosswise into two compartments which communicate with each other. In the Siluroid fish I'augasius the air-bladder is said to be divided into four portions longitudinally. Sometimes the SWIMMING BLADDER OF CARP. air-bladder develops blind processes: in certain cases from the fore part, in others from the hind part, and occasionally from both ends. In the family Sciienidse the air-bladder often has numerous lateral branches which themselves ramify into digit-like processes. In some species of the genus Gadus processes given off from the air-bladder line excavations in the transverse processes of the abdominal vertebrse, thus, as Professor Owen has pointed out, foreshadowing the pneumatic con- dition of the bones in birds. In other fishes — such as Callicluhys lucida— the aii'-bladder is even more singularly developed, since its many branches form a covering round the abdominal viscera. The wall of the air-bladder is often shining and silvery; occasionally the intei'ior is subdivided into small cells: this condition may be. seen in the genera Erythrinus and Amia. The air-bladder here seems to be taking on some of the characters of a lung, and in Lepidosii'en and Oeratodus the transition is com- pleted. The air-bladder is entirely wanting in the Sharks, Rays, Chimsera, Lampreys, Flat-fish, and other forms, several of which, like the Angler, live habitually at the bottom of the sea. The duct connecting the air-bladder with the oesophagus seems to be the rudiment of the trachea, though it does not always open into the anterior end of the aii--bladder. In most fresh-water fishes the air-bladder is filled chiefly with nitrogen gas, mixed with a little oxygen, while in sea fishes the gas is chiefly oxygen, with a little nitrogen. Occasionally, when fishes are brought up from great depths, the aii'- bladder expands, and forces the internal organs out of the mouth. In the Gurnards the air-bladder assists in the production of sound, so that these fishes may be said to possess a voice. The blood in fishes is red, but small in quantity. The red blood discs usually have an elliptical shape, and are largest in the Sharks. In the Lamprey the red cori)uscles are nearly ISTia-VTlliE OF FlSUE.'i. 15 circular; there are also, as m higher anil lower animals, larger white corpuscles. The greatest quantity of blood is found in the Tunny, which, according to Dr. Davy, is a warm blooded anim:'l, with a temperature as high as that of most mammals. The lowest type of fi.sh — tlie Lancelot — has no true heart, but a bloodvessel which pulsates very slowly, there being but one beat in a minute, while in most fishes the number of bea-ts in a minute varies from twenty to twenty-four. The heart is relatively small in all fishes, and even in Sharks and Rays is only about one-thousandth part of the weight of the body, which is about one-half of its relative size in reptiles. This organ ill fishes consists chiefly of two parts, which correspond to the pulmonary side only of the heai-t in man, and are named the auricle and ventricle. It is usually placed in the throat, in a cavity partitioned off by a fixed tendinous diaphragm. Tlxfi: auricle, which is thin and relatively large, receives its blood from a sinus, formed by the miion of the veins which bruig the blood from the body. Each aperture of the auricle is guarded with strong valves. The ventricle is small and muscular; its form is pyramidal in the Ganoid fishes, lozenge-shaped in the Pike, oval in the genus Lophius. It opens by means of valves into an enlarged muscular portion of the branchial artery, which is called the bulbus arteriosus ; this contracts like the ventricle, and assists in forcing the blood into the gills. In the interior of this organ there is an elaborate system of valves, which are arranged in two rows in most Sharks, and form three, or even six, rows in Ganoids. After the blood has passed through the gills the vessels unite and form an artery, which extends under the vertebrae along the length of the body. The modifications of the gills ai-e sufficiently important to give names to some of the great group of fishes, such as Marsipobranchii, Lophobranchii, and Elasmobranohii. In the Hag, which is an example of the Marsupial type of gill, there are six little branchial sacs on each side ; these are produced into short tubes on both sides, and these tubes are prolonged into a longitudinal canal, which extends backward, and carries the stream of water away from the gills on each side, terminating on the ventral surface on each side of a third larger opening, which admits water in the same way into the branchial sacs. In the Lophobranchii, which comprise the Pipe-fishes, the gills, initead of having the comb-like form usual among fishes, form a double series of nearly circular tufts. In the Elasmo- Ijranchii the gills are an-anged side by side, so as to suggest the idea of plates with opening.s between them, which are usually long slits, as may be seen in the Sharks and Rays. The branchial chamber is largest in those fishes in which the outlet from it is small. In some of t!ie Eels these outlets approximate close together on the under side of the head ; in the Sturgeons and Ganoids there is a canal leading from the fore part of each side of the branchial chamber to the top of the head. These canals are called spiracles. In all the osseous fishes there is only one visible outlet to the gills on each side. Each leaflet of the gUls usually consists of a pair of processes, but in some osseous fishes some of the branchial arches support only one series of these leaflets. Many genera, like Zeus .and Polypterus, have on each side three double gills and one uniserial In the genera Lophius and Diodon there are thi-ee bi-serial gills ; in Lepidosiren there are bi-serial gills and one uniserial. The number of plates on a single leaflet may range from as few as fifty-five in the Gudgeon to sixteen hundred in the Sturgeon. It is interesting to i-emark that in the embryonic osseous fish the five interspaces between the hyoid arch and the fi^e branchial arches are exposed on the sides of the head, and that subsequently the branchiostegal appendages are developed, and a single branchial outlet results from the formation and backward growth of the operculum. Owen remarks that the mechanism of breathing in fishes differs from that of swallowing only in the streams of water not entering the gullet, and being diverted to the branchial slits on each side of the pharynx. The bones which cover the gills are collectively known as the operculum. This organ is connected with the skull by means of the hyo-mandibular bone, which also supports the jaws. The principal bone is named the operculum, below which is the sub-operculum, and below this the inter-operculum. In front of these is the pre-operculum. It is necessary to complete our knowledge of fishes to carefully examine the characters of then- fins. In the majority of fishes there are five kinds of fins, which ai-e named pectoral, ventral, anal, dorsal, and caudal (see p. 3). The pectoral and ventral correspond to the arms and legs of higher animals, and when they exist they are always in pairs. The other fins are single or unpaired, and are entirely unrepresented in the skeletons of higher Vertebrates. The pectoral fins are almost always present. 16 XATlTxAL HISTOJRT. though they ai-f wanting in Lanii)reys. They are always formed of flexible rays, which are generally branched. The first ray is sometimes strong and spiny, and among Sihiroid hshes is barbed on one or both sides. In the Flying-iish, the Tunny family, and the Rays the pectoral tin attains its greatest development, and is usually pointed; but, as Swainson has remarked, families which live in rivers and lakes have the pectoral fins rounded. The Gurnards have the pectorals greatly developed, but their fins are nearly always rounded, though they may be pai-tially cleft or digitate; when broad at the base they usually extend under the throat. The cleft fins ai-e seen in the genus Cepbalacanthus; the digitated pectorals are seen in the Gurnards. The pectoral fins of Sharks are generally large. In the Flat-fish they are smaller than in any other memlier of the class. In the fiimily Pediculati, or Fish Frogs, the pectoral fins perform the office of feet. The ventral fins are less important in swimming than the pectoral ; they are generally of small size, though in the genus Zeus they are larger. In the Eel group they are entirely absent. The position of these fins varies, being placed under the throat in the Star-gazer ( Uranoscopus), while in the genus Polypterus they are neai- the base of the caudal fin. When the pectoral is rounded the ventral is usually rounded too, though this correspondence between the fins is by no means universal. Some fishes possess fins which are capable of adhesion by suction. The family Gobiesocidse has circular concave discs ou the breast and belly, which extend between the pectoral and ventral fins. In the genus Rf<;;ileeus, or Ribbon Fish, the ventral fins have the rays broadened at the extremity so as to rfsemljle oars. The dorsal fin is rarely altogether wanting, though it is absent from flyiiiiKitiix liraiirliin nis. The dorsal fin is generallj' composed of a number of bony rays, placed successively Ijehiud each other and connected by a membrane. Frequently there are two dorsal fins. In the soft-finned gi-oup the hinder dorsal fin is generally formed of fat. The Polypterus offers a remarkable type of dorsal fin, in that the fin is divided into a large number of finlets, which reach from the head backwards. The dorsal fins are very thick in cartilaginous fishes, and are thinner in the spiny-finned osseous fishes. A few genera have three dorsal fins, as may be seen in the Cods. The rays forming the fin are sometimes slender bones, are sometimes jointed, and sometimes branched. The branched spines are well seen in genera allied to the Mackerel. The common Stickleback furnishes a familiar example of the spiny modification of the fin. Sometimes the dorsal fins are triangular, and sometimes they are broad, and occasionally end in filaments. In a good many fishes, e.specially among the Eels, the dorsal fin unites with the caudal fin. The anal fin corresponds more or less to the dorsal, only it is placed longitudinally on the inferior mai'gin of the body, behind the vent. Sometimes, as in trymnotus, it extends nearly the whole length of the fish. The caudal fin is the great organ of motion; it usually consists of two symmetrical lobes, which are made up of a number of radiating i-ays. The terminal part of the notochord, or spinal column, as the case may be, bends upward, so that a larger number of the fin rays lie below than above it; hence, although the tail in the bony fishes is homocercal in form, it is heterocercal or unsymmetrical in structure. In the Tunny the tin rays are attached to the sides of a somewhat fan-shaped terminal bone, and in these fi.shes the tail is more deeply forked than in any other. The caudtil fin presents every modification in form ; it is lanceolate in the Indian Gobies, but is sometimes rounded, or truncate, oblong-oval, even, and variously forked. Occasionally the caudal fin is indistinct ; it is but little developed in the Rays, and there is no terminal fin in the Pipe-fish or in Chimsera. In one genus the fin is placed vertically upon the extremity of the tail. The analogy of fins to wings is evidenced by their parforming the office of wings in the Flying-fishes. One of the best characters by whicli the genera and species of fishes may be identified and defined is furnished by the number of rays in the several fins. In most cases these are written in formiilse, in which the number of rays in a fin follows its initial letter. All fishes have the sexes distinct. The male organs con.stitute the well-known soft roe, while the ovary of the female is hard roe. In the female the oviduct has its outlet usually in front of the urethra, and behind the anus. In the Californian genus Ditrema the young reach a relatively large size, and are packed in the body of the parent as close as Herrings in a barrel. The oviparous cartilaginous fishes are remarkable for the large size of the egg, and the strength of the case in which it is contained. In Sharks of the genus Cestracion this egg-case is spiral ; and in the southern Chim. Sub-Order II.— Pleuronectoidei. Family VII.— Pleuroneclidaa (Flat Fishes). ORDER IV.— PHARYNGOGNATHI (FISHES WITH JAWS IN THE THROAT). Family I. — Pomacentrida\ II.— Labrid;e (Wrasse). III. — Embiotocidie. IV.— Gerridaj. V. — Chromides. ORDER V.-ACANTHOPTERYGII (SPINY-FINNED FISHES). Family I.— Percidie (Perch). II.— Pristiporaatida;. III.— Squamipinnes. IV.— Nandidie. V.— MulUdai (Red Jlullet). VL— Sparida^ VII.— H"plon;nathida3. VIII.— CiiThitida;. IX.— Scorpajnina. X.— Polyccntrid;e. XL— Teuthidida;. XII.— linvci-l:,'. "XIII.— Kurtid:e. XIV.— Polynemida?. XV.— Sciajnidae. XVI.— Xiphiida3. XVII.— Tiirhiuiiil.. 1 Haiitoils). XVIII.— Acronuridaj. XIX— Carangidae. XX.— Cj'ttina. XXI.— Stromateina. XX 1 1. — (Mrvi.lLiuiiia. XXIII.— Nomeina. XXIV.— Seombrina. XXV.— Trachinida'. XXVI.— Malacanthida?. XXVII. -Batrachida\ XXVIII.— Pcdiculati (Sea-devil). XXIX.— Cottina (Gurnards). XXX.— Cataphracti (Aniicd Bull-head). XXXI.— Comcphorida'. XXXII.— Discoboli (Lump suckers). XXXIII— Gobiida!. XXXIV.— O.xud.rcida;. XXXV.— Cepolida-. XXXVL— Trichonotida\ XXXVIL— Heterolepidina. XXXVIII.— Blcnnii.he. XXXIX.— Acanthoclinida\ XL.--Mastacembelid8e. XLI.— Sphyrajnida;. XLIL— Atherinidie. XLIIL— JIasilid;e (Grey Mullet). XLIV.— Gasterosteida) (Sticklebacks). XLV.— Fistularida;. XLVL— Centriscida^. XLVIL— Go'biesocida; (Suckers). XLVIIL— Psychrolutidaj. XLIX. — Ophiocephalida;. L.— Labyrinthici (Climbing Perch). LI. — Luciocephalida;. LII. — Aphredoderidas. LIIL— Lophotidie. LIV.— Trachypteridie. LV.— Notacanthi. ORDER VL— PHY'SOSTOMI (FISHES WITH THE AIR-BLADDER OPENING INTO THE MOUTH). Family I. — Siluridse. II. — Characinidas. III. — Haplochitonidoe. IV.— Sternoptychidas. V.— Scopelidaj. VL — Stomiatida>. VII. — SabivmidiP ^Snlmon'i. VIII. — Percopsida?. IX. — Galaxida;. X. — Mormyrida?. XL— Gymnarchidaj. XII. — EsMri.ln' 'Pik.'. XTTI— Umbridaa. XIV.— Soombresccid*. XV. — Cyprinodontida-. XVI.— Heteropygii. XA'1 1. rvi.rii.i,!,.- r.-vy). XVIIL— Gonorhynchida;. XIX. — H vodontida\ XX.— Osteoglossida;. XXL— < luii. ia.r , II, uiu-- . XXIL— Chirocentrida;. XXIIL— Alepocephalida?. XXIV.— Notopteridaj. XXV— Hulo.-aund.e. XX\I.— (iymnotida; (Electric Eel). XXVII.-Symbranchida?. XXVIIL — lMura3nida3 (Eels). XXIX. — Pegasidas. DIVISION III.— CYCLOSTOMATA (FISHES WITH A CIRCULAR MOUTH). ORDER.— MARSIPOBRANCHII. Family I. -Petromyzontidaj (Lamprey). II.-Myxinida3 (Hag). DIVISION IV.— LEPTOCARDII (FISHES WITH A THIN HEART). ORDER.— PHARYNGOBRANCHII. Family.— Cirrostomi (Lancelot). CHAPTER II. THE PAL.EICHTHYES, OR FISHES OF ANCIENT TYPES. DIPNOI OR MUD-FISHES— Why this Order is Interesting— The African Mud-fish— The South American Mud- fish—The GENUi Cekatodus-GANOIDEI, OR FISHES WITH BONY SCALES-The AsiliDJi— ^ //i/a calca- The Bonv Pike of the Nile— The American Bony Pike — Its Remarkable Characters —HOLOCEPHALA — The Chimicra nionstrom—The Genus Callorhynchus -PLAGIOSTOMATA— The Sharks and Rays— Selachoidei— The Blue Shark— Its Habits— Muscular Vitality— Economic Uses— Other Genera— The Common British Tope— The Hammer-headed Shark— The Smooth Hound— The Porbeagle, or the Beaumaris Shark— The Thresher, or Fox Shark— The Basking Shark —Enormous Proportions -The "Sea Serpent"— Habits— Fisheries— Characters-THE Six-GILLED Shark— Thf, Dog FiSHES-The Nurse Hound and the Rough Hound-Their Eggs and Egg-purses— "Sea-dog Soup"— The Black-mouthed Dog-fish— Cestracion— The Picked Dog-fish -Why so Named— Characters- Various Forms-THE Spinous Shark-The Monk-fish— The Indian Shark Oil Industry-BATOIDEI, THE RAYS —Distinctive Features— The Phistid^— The Rhinobatid.e-The Torpedinid.e— The Genus Torpedo— Strength of the Shock— The Electric Organs— Characters— Other Forms -The B.\vs- Characters -The True Skate -Fishery- The Long-nosed Skate— The Bordered Ray— The Shagreen Ray— The Homelyn Ray— The Thorneack— The Sting Rays— Growth of its " Spine "—Various Species— The Eagle Ray— The Ox Ray, or Sea Devil— CHONDROSTEI— The Sturgeons— Characters -Caviare -Fishery-Other Economic Uses— The Common Sturgeon- Article of Diet- The Anpemer huso-The Sterlet— The Paddle-fish. DIVISION I.— PAL^ICHTHYES. ORDER I.— DIPNOI.-MUD-FISHES. Tins small group of fishes has more than ordinary interest, from the circumstance that it com- prises surviving representatives of a large fish fauna, now entirely extinct, which abounded in the early periods of the earth's history. And yet, instead of presenting, as might have been expected, characters of immature or imperfectly-developed forms, these fishes are the only ones which make an appreciable appi'oxiniation in structure to the Amphibia. FAMILY SIREXOIDEI. There are only three genera ^novm—Protopterus, limited to Africa, Lepidosiren to South America, and C'erafudits to Australia. GENUS PROTOPTERUS.— THE AFRICAN MUD-FISH. But one species is known, the Protoptems miiiectans', which has an Eel-like form, grows to a length of three feet, and is found in the Nile, the Zambesi, and the Gambia. It has been brought alive to Great Britain enclosed in balls of hardened clay, in which the fish hibernate and remain torpid during many months of the year, with a small hole in the clay at each end to admit the air. They are abundant in the rice-fields, where they are dug out of the mud by the natives, who regard them as a delicacy. The examples originally described liy Sir R. Owen were twelve or thirteen inches long, and measured about four inches and a half round the body. The head was two inches long, and the distance from the pectoral to the ventral fin five inches and a half The muzzle is blunt, and the head gradually enlarges towards the gill-opening, which is just in front of the base of the pectoral tin or fore-limb. A line of mucous pores surrounds each eye, and from this the lateral line com- mences, and is prolonged down the body to the end of the tail, making a slight downward curve towards the ventral fins. There is a membranous dorsal fin. The body is sheathed in scales of the cycloid pattern, which are arranged in about sixteen longitudinal series on each side of the body. Each scale is marked by a number of canals, which radiate from a centre near the posterior edge, and are connected by cross canals. The bones are green, like those of the common Garfish. The vertebral column i-etains the primitive condition seen in the early stage of development of all animals in which the continuous cylindrical, somewhat gelatinous rod, which is termed the notochord persists, in the position which usually becomes occupied by the bodies of the vertebi'iB, a change which is brought about by the deposition within the notochord of the salts of lime which form bony matter. Here the notochord has merely an external sheath of ligament, except towards the tail, where it becomes somewhat cartilaginous. The neural arches, however, wliich cover the spinal cord, are con- verted into bone, and are prolonged into neural spines, each of which articulates with a bone above, which bones form the base of the dorsal tin. Theie are thirty-six pairs of simple ribs, which are all of TUE AFKICAN MCD-FlVH. ID about tlie same length, and all short ; they are bent downward in the tail, so as to form an inferior arch like the.neni"al arch, after the manner which is usual in, fishes. The skull is penetrated by the cranial end of the notochord, though it there becomes ossified. The skull is divided into distinct cranial segments, each formed of bones. The lower jaw consists of two pieces — a dentary bone in front and the articular bone beliiud. The jaws are armed with two slender conical teeth on the pre-maxillary bones, and with a strong dental plate on both the lower and uppin' sides of the mouth. These teeth are marked with ridges, and were originally compared by Sir K. Owen to the teeth of Ceratodus — then .supposed to be extinct — and the teeth of Chiman-a. Tliere are no teeth on the bones of the palate. The intestine is straight and short ; it terminates in a spiral valve formed of sLx gyrations. The vent does not open in the middle line of the body. There is no trace of a pancreas or .spleen, but the dark-brown liver has a gall-bladder in a notch of its left margin. The bile is conveyed by a duct into the intestine. The brain closely resembles that of Amphibians. This genus is di.s- tingjiished ' by possessing six branchial arches with five intervening clefts, and has three small branchial appendages above the small gill-opening. The air-bladder has a longitudinal partition, so as to divide it into two elongated sacs, which are supplied with venous blood from a pulmonary artery. Each of these sacs is divided into cells, which are more numerous in tin' fore-part of the bladder than in the hinder part. It is by means of these incipient lungs tluit ivspiiation is carriea on during the dry months, when the animals live out of water. Air is intiuihucd directly into the- air-bladder, and the opening of the duct from it into the cesophagus is kept distended by a cartilage like a rudimentary larynx. When, in the wet season, the Lepidosiren resumes life as a fish, the branchial circulation again goes on vigorously, but the animal still rises to the surface and swallows air. The Protopterus exhibits the simplest form of limb which is known. The pectoral and ventral 20 NATURAL HISTOKY. fins or limb eacli consists of a single ray which tapers to a point, and is joLnted much like a single- jointed fin-ray of an ordinary fish. These limbs are attached to arches which rei)resent, in an imperfect condition, the cori'esponding pectoral and pelvic girdles of osseous fishes and amphibians. GENUS LEPIDOSIEEN.— THE SOUTH AMERICAN MUD-FISH. Lepidosiren was discovered in the River Amazon. It so closely resembles Protopterus in the form of its body that for a long time the two species were placed together in the same genus. The Lepidosiren paradoxa, however, has but five branchial arches with four intervening clefts, has 110 trace of the external branchial appendages, has no fringe to the pectoral and ventral filaments, -such as is seen in Protopterus, and has about fifty-five pairs of ribs. In this animal the eyes are small, and the skin passes over them. The species reaches a length of three feet, and when the waters dry up on the tributaries of the Amazons the fi.shes plunge into the mud. Sir Eich. Owen remarks that Lepidosiren is proved to be a fish not by its gills, nor by its air- bladder, ncr by its spiral intestine, nor by its unossified skeleton, nor by its extremities, nor by its eyes, nor by its ears, but simply by its nose. For the organ of smell in every fish is a shut sac, communicating only with the external surfixce ; while in every reptile it is a canal with both an external and an internal opening. So that we arrive at the unexpected result that a reptile is not characterised by its lungs, nor a fish by its gills. THE GENIUS CEEATODUS. A few years ago Mi". Gerard Krefl't announced that there was still living in the rivers of Queensland, in the north-east of Australia, a fish with teeth which so closely resembled those of the fossil Ceratodus from the older Secondary rocks, that he was compell'ed to refer it to the same genus. It is stated to occur abundantly in most of the rivers, and is known locally among Europeans as the Flat-head. At night it is believed to leave the streams, and go out among the reeds and rushes on the flats, wliich are left uncovered at low tide, and it is said often to be heai'd moving on still nights on the banks of the River Mary. In some localities it goes up the river only as far as the water remains brackish, but other specimens have been captured in fresh water thirty miles inland. Individuals are said sometimes to reach a length of six feet. The intestines are always found crammed full of dead leaves, which belong to the natural orders of plants Myrtacese and Gramiuse. In external shape the Ceratodus has a close likeness to the Lepidosiren, except that it more nearly resembles an ordinary fish, has stouter paddles, and large scales covering the body. The head is longer than it is wide, but broad and flattened, with a short snout. Its upper surface is covei-ed with a thick skin pierced by small pores. The gill-cover and throat are clothed with scales like those on the body ; the eye, which is small, is near to the snout ; the corners of the mouth are in front of the eyes, and the lips are thick and soft. The whole body is covered with large scales, which have faint concentric lines of growth, but towards the end of the tail the scales become rapidly smaller, and small scales cover nearly the whole of the terminal fin. The central portions of the fin-paddles are also covered with small scales. The lateral line is marked in the usual way ; from the head to the region of the vent there are twenty-two large perforated scales in this line, and beyond that point there are about , seventeen smaller scales. In the middle region the body is encircled by eighteen or twenty rows of ■scales, of which only one-third arc above the latei-al lines. The limbs, like the tail, vary a good deal in appearance ; they taper to a fine point, the front pair being longer than the hinder pair, which latter are given oflf just in front of the vent. Nearly all the skeleton is cartilaginous, but in Some regions of the skull the cartilage is sheathed in thin bony tissue. Dr. Giinther describes it as a complete inner cartilaginous capsule, covered with an incomplete outer osseous case, to which some •cartilagmous elements are attached. The skeleton of the branchial apparatus is formed of fine arches, and though entii-ely cartilaginous, is similar to that of ordinary bony fishes. The vertebral column is remarkable for retaining a condition which is usually found only in the early embryonic •development of the higher vertebrates, for there is no complete division of the central gelatinous rod called the notochord into separate vertebras. Upon this notochord are developed about sixty- ■eight sets of arches, which extend above it to enclose the spinal cord, and below to support the • blood-vessels. Twenty-seven of the lower arches behind the head carry ribs. The teeth are fitted for TUB a.l\OJD FJS}r£S. 2i cutting and crushing. Tliere is one jiair of snmll teeth in the fore-part of the jaw wliicli, from thcii- positiou upon a bone called the vomer, are termed vomerine teeth ; they meet each other at a right angle, which is directed forward. The' other teeth are much larger, and are crossed by six strong ridges, which extend inward from the outer margin. Between these ridges are five notches. In a specimen three feet long this tooth is an inch and a quarter long and half an inch wide. The coi-- responding teeth in the lower jaw have a similar shape, and are so placed as to fit against the- others and form an apparatus for grinding food. The hard parts of the fore-limb are entirely car- tilaginous ; the paddle is joined to the scapular arch by a cartilage which represents the humerus. A median row of cartilages of a quadrate form, twenty-six in mnnber, extends the length of the- limb, and on both sides of it rays are given ofi" which diverge downward and outward. This type of fin is quite unpai-alleled, although the central series of cartilages may be compared to that- of the Lepi- dosiren. Dr. Giinther ha.s compared the fin to the tail of an ordinary os.seous fish ; nor is the plan of structiu-e very dissimilar to the tail of Ceratodus itself. The structure of the hind-limb is quite like that of the fore-limb, except that it is rather more symmetrical and is shorter. The intestine- is nearly straight, and below the stomach is traversed throughout by a spiral valve, which may be compared to that of Sharks and Rays, and winds around nine times. But the most remarkable circumstance about this fish is the fact that it can breathe either by gills or by lungs, or simul- taneovisly by both. The gills are not connected with spiracles, nor is there any true operculum. The- lung is single, and is a wide sac which extends down the middle of the dorsal region, from one end of the abdominal cavity to the other. It is divided into about thirty compartments on each side, and in these the tissue presents much of the character which is usually seen in the lung of an-eptile. It has a short duct terminating in a glottis, which opens on the ventral side of the gullet. The air is probably expelled from the lungs much as among i-eptiles — by the tissue contracting ; and this is thought to account for the grunting noise heard at night when the fish are out of watei'. The species has been named Ceratodus forsteri. CEKATODUS. {After Guniher.) OEDER II.— GANOIDEI, OR FISHES WITH BONY SCALES. FA3[ILY I.— AJIIID.E.— THE NORTH AMERICAN MUD-FISH. The Ganoid fishes are a group fast verging on extinction, and are represented at the present day by three families, which include four genera and six species ; but from the light which their structure throws on the fossil forms of both Primary and Secondary strata, no less than from some remarkable points of structure, they deserve notice. In the first fiimily, Amiidae, there is but one species — Amia calva, which is known as the Bow-fin of Lake Champlain, the Dog-fish of Lake Erie, the Marsh-fish of Canada, and is sometimes known as the Mud-fish. The body is long, com- l)ressed behind, and sub-cylindrical. The head is broad, with a short snout; the jaws are margined with an outer series of delicate sharp-pointed teeth, which are closely set, and there are patches of similar teeth on the vomer, palatine, and pterygoid bones. The lower jaw has a single row of 22 NATURAL HISTORY. teetl). The tongue is covei-ecl with papillse ; the. nostrils are prolonged into short tubes. The scales are of the cycloid pattern, and are sometimes covered with enamel ; they are large, and marked with radiating lines, and are enveloped in a soft skiji ; those which occur in the lateral line are slightly elevated. The colour is dull, often dark greenish, with black spots and bands, and there is fre- quently a round black spot on the tail. The animal is covered with thick mucus. Its movements in the water are not very rapid. It feeds chiefly on fresh-water Crustacea, is sometimes eaten by the Indians, and attains a [ength of about two feet. The vertebral column is chiefly remarkable for having intercalary vertebrae introduced in the tail. The first appears after the sixth caudal, and the last between the twenty-second and twenty-third caudal. These intercalary bones are entirely devoid of processes, and occasionally one or more of them may be absent. The end of the vertebral ■column is cartilaginous, and directed upward. The air-bladder is a large membranous sac divided anteriorly into two short horns ; its internal appearance is compared to that of the lung of a serpent with cells in the anterior part which disappear towards the posterior end. It communicates with the cesoph^gus by a duct, and has a sort of glottis with an oblong opening. There are four gills; each arch is formed by a double row of leaflets ; there are ten or twelve branchiostegal rays. The .stomach forms a blind sac, diverging from the intestine; there are no pancreatic appendages; the liver has two lobes ; and there is a rudimentary spiral valve at the termination of the intestine. This fish is limited to the fresh waters -of the United States, and is especially met with in the great e,vpanse of low-lying country between the Alleghanies and the Rocky Mountains, in the Mississipjti, Nor- thern lakes, and Middle States. FAMILY II.— POLYPTEIIID.E.— THE BONY PIKE OF THE NILE.* This is the type of a family wliich at the present day includes only two genera. Polypterus occurs throughout the tropical parts of Africa, especially in the Nile, Gambia, and Senegal rivers, and other parts of the west coast. It is an elongated fish, with a short snout and somewhat cylindrical bod3'. It is defended with lozenge-shaped ganoid scales. The species Polypterus bichir lives in the mud at the bottom of the rivers, where the fish crawl or walk like Seals by means of their tins. They swim with great rapidity, much in the manner of serpents. At the time of reproduction they are chiefly at the surface of the water. This fish presents an extraordinary appearance, from the way in which the dorsal fin is broken up into a succession of little finlets, which vary in number in the several varieties from eight to eighteen. The vertebra} are bi-concave, as in ordinary fishes, but the termination of the vertebral column is cartilaginous. The head is covered by enamel similar -^'-^^-a,'-^^^.'^^^ to that which defends the scales of the trunk. From the lateral expansion of the bones of the head, this fish presents much the same sort of resemblance to a Chelonian that the head of the Lepidosteus has to that of a Crocodile. The ventral fins are well developed, and the anal fin is placed close to the lower margin of the caudal fin. The central portion of the fin in these fishes is fleshy, and covered with scales, so that the rays appear as a fringe around it. This character is met with in many of the fishes of the Old Red Sandstone, and Professor Huxley has proposed to unite them together under the name of Fringe-finned Fishes, or Crossopterygidse. There are three bones between the tin rnys and the shoulder-girdle. The air-bladder is more simple than that of Lepidosteus ; it oinisists of two sacs, which are cylindrical and unequal, but there are no internal cells in the bladder representing lung structure. There is, however, a duct from the two lobes oj)ening into the oesophagus, and the opening is defended liy a circular muscle. There are three and * Genus Polypterus. JIIE AMERllAN JiU.M' i'lKE. -23 a-lialf paii-s of gills, but no gill uiioii the operculum. There is a spiracle on each side of the parietal hone, covered by a bony plate. The branchiostegal rays are replaced by a single plate of bone. The stomach has no blind sac, there is one pancreatic appendage, and tlie intestine terminates in a .spiral valve. There are fifty-one vertebra; in the abdomen and sixteen in the tail. From Old Calabar there comes a remarkable fish closely allied to the Polypterus, which is named Calamoichthys calabaricus. It has a much more elongated form ; the dorsal and ventral sur- faces are parallel. There are about a hundred vertebrae in the abdomen and ten in the tail. The dorsal fin is represented by from nine to eleven fiulets ; the ventral fiu is absent, and the small anal fin is placed at the hinder extremity of the body, immediately below the tail. FAMILY III.-LEriUOSTEID.E.— THE AMERICAN BONY PIKE.* The Bony Pike, or Garfish, as it is often called, is one of the most distinctive of American types of fish-life. It is met with in the rivers and lakes of the basin of the St. Lawrence, in various parts of the United States, and in Mexico, and occui's in Cuba. American authors have distinguished more than twenty different species, which have been referred to several genera. Dr. Giinther reduces these species to three — the Lepiclosteus viridis, the Lepidosteus platystomus, and Lepidosteus osseus. These fishes swim with the greatest rapidity, darting through the lakes and rivers, and are able to pass through the most rapid currents, not excepting the rapids of Niagara. Their bodies are more flexible than those of ordinary fishes. Agassiz notices that the liead moves freely on the neck, and may be indifierently wagged from side to side, or moved upward or down, movements which are impossible in other fishes. This mobility results from the remarkable mode of union of the vertebra; with «^ach other. Instead of being cupped at each end there is a rounded articular surface in _f ront, and a corresponding concavity behind. The vertebral column terminates in a small conical cartilaginous rod, which is directed to the upper margin of the tail, where it is only covered by the skin. The vertebris luue transverse processes, to which the ribs are articulated. The head has an armoured appeai-ance, and is covered with furrows and rugosities, which are arranged in a definite manner ; it is prolonged into jaws, which are lai-ge and long in proportion to the size of the hinder part of the head. The lower jaw is always rather shorter than the upper, and is formed of the .same bones as occur in the jaws of Crocodiles and Lizards. The maxillaries are a series of bones joined together, end to end, so as to produce by their union a single long bone. The snout includes, besides the maxillaries, long nasal bones and some other bony elements. The fins unite with the skeleton, as in other osseous fishes. The pectoral fins are strongly developed. All the fin-rays are jointed. The air-bladder is placed as in other fishes; it communicates with the throat by a duct, which is guarded by a circular muscle. This organ is very long, and extends from the tesophagus to the hinder extremity of the body. It is forked in front, but is undivided in the greater part of its length, and sometimes there is a trace of a posterior bifurcation ; it is said to be muscular, so as to be capable of contracting. Its internal surfiice is cellular, so that it presents some resemblance to the lungs of the lower reptiles and amphibians ; but wliile air is breathed by this organ there are also gills, whic"h are supported on four arches and have a bi-serial structure. The brancliiostegal rays are three in number. The scales, next to the long jaws, aie the most striking feature of the animal. They are lozenge-shaped, and arranged in more or less oblique series, so as to overlap each other, and form a close-fitting bony armour. In the middle of the belly the scales are heart-shaped. The external layer of the scales is always brilliant and shining, being formed of enamel, while the lower laj-er consists of bone. The scales are perforated by canals similar to the blood-vessels in bones, and the vessels passing through them carry blood to the skin. The lateral line is always straight. The colour of the back is brownish-yellow or greenish, sometimes with black spots. The young sometimes have a dark band at the sides, and generally a dark baud m the median line of the back. The nasal pores are at the extremity of the snout, and the eyes are a moderate size. These fishes are extremely voracious ; they often frequent shallow and reedy places and bask in the sun. They approach their prey slily and sideways. The prey is lield in the mouth * Genus Lepidosteus, 2i KATVE.1L MISrOIiY.