Org"ns,vital,57Origin of alimentary canal,444Ori"in ofarthropods from annelids,395Ori"in ofatrial cavity,409Ori"in ofauditory capsules and parachordals,377Ori"in ofcœlom,475,481Ori"in ofductless glands,428Ori"in offree cells,472Ori"in ofheart of vertebrate,179Ori"in oflateral line organs,356Ori"in ofmuscles,478Ori"in ofmusculature, branchial,170Ori"in of muscul"ture,somatic trunk,406Ori"in ofnervous system, central,480Ori"in ofnotochord,434Ori"in ofsegmental excretory organs,389Ori"in ofskeleton of vertebrates,119Ori"in ofvertebrates,9,36,351,433,493Ostracodermata,326,343Osteostraci,29,75,275,326,343Otoliths,378Ovum,473Pacinian bodies,470,477Palæmon,20,422Palæontology, evidence of,20,497Palæostoma,317Palæostraca,27,396Palæo"traca,median eyes,74Palæo"traca,mesosomatic appendages,188Palæo"traca,olfactory organs,221Palæo"traca,segments, compared to Ammocœtes,308Pantopoda, glands,423Parachordals,121,132,377Parapodia,357Parapodopsis, foot glands,422Parathymus,427Parathyroids,427Parietal organ,76Pecten of scorpion,114,359,366,371,372,373,374Pedipalpi,190Periblast,471Peripatus,396,399,400,411,421,429Petromyzon, alimentary canal,405,445Petro"mzon,auditory organ,378Petro"mzon,branchial segments,169Petro"mzon,life-history,59Petro"mzon,olfactory tube,219,226Petro"mzon,pronephric duct,402Petro"mzon,retina and optic nerve,95Petro"mzon,skeleton,125Petro"mzon,suctorial apparatus,287,304Petro"mzon,transformation,v.Transformation of the LampreyPhagocytes,420,471Pharynx of Amphioxus,410Phar"nx ofVertebrate,440Phoronis,439Phrynus, brain,53Phry"us,caudal brain,450Phry"us,carapace and carapace removed,250Phry"us,cœcal diverticula,109Phry"us,evidence of segmentation of carapace,249,250,341Phry"us,operculum,191Phry"us,prosomatic appendages,306Phry"us,crossing of dorso-ventral muscles,271,277Phry"us,stridulating apparatus,368Phyllodoce,395Phyllopoda,321Pigment, in Ammocœtes, in position of atrial cavity,412Pigm"nt, inepithelial lining of central nervous system,43,457Pigm"nt, inchoroid of vertebrate eye,104,107Pigm"nt, inbetween glandular cells round brain of Ammocœtes,211,379Pigm"nt, intapetal layer of retina,70Pigm"nt, inwhite, of right pineal eye of Lamprey,76,80Pineal body,14,15Pin"aleyes,74,233,244Pin"al ey"s,of Ammocœtes,80,78,85Pin"algland,63,75,456Pits, epithelial, of diaphragms in Ammocœtes,164Pi"t, epith"lial, ofskin in Ammocœtes,173,200Pituitary body,244,246,319,321,425,430Plasma-cells,471Plakodes,283Planarians,475Plastron, formation of cranial walls from the,86,322,341Plat"ron,of Limulus,136,142,143Plat"ron,Palæostracan, compared to trabeculæ of Ammocœtes,145,377Plat"ron,muscles attached to the,270Plat"ron,of Thelyphonus,143Platyhelmia,475Pleuron,410,415Plexus, of Auerbach,447Plex"s, ofchoroid,38,45,49,103Plex"s, ofhypogastric,3Polychæta,357,395Pores, abdominal,430Porifera,473Pouch, formation of gill,165,166Prestwichia,24,25,249,351Principle of concentration and cephalization,51Prini"ple ofembryology,455Pristiurus,424Progress, law of,19Progr"ss,result of,56Pronephros,389,397,419,424,449Prosencephalon,48Prosoma,52Protopterus,148Protostraca,27,396,417Proto"traca,dominance of,28Protozoa,166,479Pseudoniscus,25,249Pteraspis,29,30,275,326,343,344,350Pterichthys,29,31,239,326,351Pterygoid, pedicle of,295Pterygotus,25,27,56,170,191,221,235,238,249,276Ptychodera,494,495Ramus branchialis profundus of facial nerve,311Ra"mscommunicans,2,3Raphe,46Recapitulation, law of,434,456,498Regeneration of nerves,469Reptiles, dominance of,21Retina, compound,71Ret"ia,development of,101Ret"ia,inversion of, in Vertebrates,114Ret"ia,inverted,70Ret"ia,layers of compound,73Ret"ia, lay"rs ofin Crustacean eye,100Ret"ia,of lateral eye of Ammocœtes,93,95,111Ret"ia,Musca,89Ret"ia,Pecten and Spondylus,114Ret"ia,upright compound,72Ret"ia, upri"htsimple,69Rhabdites,69,81Saccus vasculosus,244,322Scales,345Scaphaspis,349Schwann, sheath of,469Sclerotomes,388Scorpion, brain,54Scor"ion,branchial lamellæ,175Scor"ion,development,482Scor"ion,entochondrites,377Scor"ion,excretory organs,397Scor"ion,eyes,75Scor"ion,lung-books,150,170Scor"ion,lymphatic glands,423Scor"ion,muscles, oblique,278Scor"ion, mus"les,recti,271Scor"ion, mus"les,respiration,171Scor"ion, mus"les,veno-pericardial,177Scor"ion,muscular system,247,268,269Scor"ion,nerves to Cheliceræ,237Scor"ion,olfactory organs,220Scor"ion,operculum of male,189,206,212Scor"ion,pecten,359,366,371,373,374,377Scor"ion,under surface,372Scor"ion,uterus,189,202,203,204,205,212Sea-scorpions,25,26,27,56,150,170,191,208,221,232,235,241,349,359Segmentation, branchiomeric,124Segmet"ation,body-muscles in vertebrate,388Segmet"ation,eye-muscles,248Segmet"ation,of head, double,155,157,173,234,258,411,459Segmet"ation,of head-shield,339Segmet"ation,history of cranial,258Segments, branchial of Ammocœtes,161,178,186Segm"nts,hyoid, in Ammocœtes, double,186,201,267,300Segm"nts,innervation of branchial,151Segm"nts,first mesosomatic, in Limulus and its allies,188Segm"nts,mesosomatic, of Eurypterus,192Segm"nts,prosomatic of Limulus and its allies,233,249Segm"nts, prosm"atic ofAmmocœtes,286Segm"nts,of spinal region of Vertebrates,388Segm"nts,of trigeminal nerve-group,257,279Segm"nts,tubular muscles of hyoid,299Sense-organs of Amphioxus,34Sense-o"rans ofbranchial, of Limulus,359,360Sense-o"rans oflateral, of Annelids,357,367Sense-o"rans oflateral-line system,356,411,470Serum,492Significance of the optic diverticula,102Silurus,488Sinus, longitudinal venous, of Limulus,176,312,451Sin"s,rhomboidal of bird,46Skeleton, Ammocœtes,126,296,335Skel"ton, Amm"cœtes,branchial,126,126Skel"ton, Amm"cœtes,basi-cranial,132Skel"ton, Amm"cœtes,muco-cartilaginous,291,296,330,331Skel"ton,aponeurotic,414Skel"ton,Cephalaspis,414,415Skel"ton,evidence of the,119Skel"ton,Limulus, cartilaginous,126,136Skel"ton, Lim"lus,mesosomatic,137Skel"ton, Lim"lus,prosomatic,142Skel"ton,Petromyzon,125Skel"ton,Vertebrate, commencement of bony,120,121Skin, digestive power of cells of, in Ammocœtes,58,442Si"n,of Ammocœtes,346Si"n,nerves of,448Skull of dogfish,123Skl"l ofpig-embryo,121Slimonia,27,56,170,235,238,249,276,303Solenocytes,395,477Solpugidæ,109Sphæroma serratum, brain,62,90,101,225Spiders, eyes,75Spi"ers,stomach,109Spina bifida,50Spinal cord, difference between brain and,45Spi"al cr"d,region of,385Spi"al cr"d,termination in bird-embryo,51Spondylus, retina of,114Squilla, eyes,100Sqi"lla,glands,422Stomach, cephalic,4,43,102,244Stylonurus Lagani,27,235,239,249Substantia gelatinosa Rolandi,44Suprarenal body,423Surfaces, dorsal and ventral,11Surf"ces,reversal of,15,29,36,87,175,352,433,484Synapse,72Syncytium,464,471,479Tail of lizards,50Tapetum,69Teleosteans,23,345,420,424Tendon-organs,470Tentacles of Ammocœtes,246,289,303Tergo-coxal muscles,247Test, biological, of relationship of animals,492Thalainencephalon,48Thelodus,344Thelyphonus,231Thely"honus,brain,53,54,56,224Thely"honus, br"in,caudal,450Thely"honus,cœcal diverticula,109Thely"honus,entosternite,143Thely"honus,genital organs,206Thely"honus,lyriform organs,368Thely"honus,olfactory passage,226,306Thely"honus,operculum,189,190,206,207Theory, gastræa,444,461Theories of the origin of vertebrates,9,411,433,457Thionin reaction,131,139,213,330,336Throat, formation of,179Thyestes,30,31,275,326,328,329,339,340,341Thymus,425,430Thyroid gland of Ammocœtes,61,127,192,194,196,429,459Thyr"id gl"ndevidence of the,185Thyr"id gl"ndfunction of, in Ammocœtes,213Tissues, connective,471,474,481Tiss"es,evolution of,19Tiss"es,notochordal,435Tiss"es,two groups of,463Tongue of Ammocœtes,246,303Tonsils,427,430Torpedo,262,392,470Trabeculæ,121,132,133,145,277,295,377
Org"ns,vital,57
Origin of alimentary canal,444
Ori"in ofarthropods from annelids,395
Ori"in ofatrial cavity,409
Ori"in ofauditory capsules and parachordals,377
Ori"in ofcœlom,475,481
Ori"in ofductless glands,428
Ori"in offree cells,472
Ori"in ofheart of vertebrate,179
Ori"in oflateral line organs,356
Ori"in ofmuscles,478
Ori"in ofmusculature, branchial,170
Ori"in of muscul"ture,somatic trunk,406
Ori"in ofnervous system, central,480
Ori"in ofnotochord,434
Ori"in ofsegmental excretory organs,389
Ori"in ofskeleton of vertebrates,119
Ori"in ofvertebrates,9,36,351,433,493
Ostracodermata,326,343
Osteostraci,29,75,275,326,343
Otoliths,378
Ovum,473
Pacinian bodies,470,477
Palæmon,20,422
Palæontology, evidence of,20,497
Palæostoma,317
Palæostraca,27,396
Palæo"traca,median eyes,74
Palæo"traca,mesosomatic appendages,188
Palæo"traca,olfactory organs,221
Palæo"traca,segments, compared to Ammocœtes,308
Pantopoda, glands,423
Parachordals,121,132,377
Parapodia,357
Parapodopsis, foot glands,422
Parathymus,427
Parathyroids,427
Parietal organ,76
Pecten of scorpion,114,359,366,371,372,373,374
Pedipalpi,190
Periblast,471
Peripatus,396,399,400,411,421,429
Petromyzon, alimentary canal,405,445
Petro"mzon,auditory organ,378
Petro"mzon,branchial segments,169
Petro"mzon,life-history,59
Petro"mzon,olfactory tube,219,226
Petro"mzon,pronephric duct,402
Petro"mzon,retina and optic nerve,95
Petro"mzon,skeleton,125
Petro"mzon,suctorial apparatus,287,304
Petro"mzon,transformation,v.Transformation of the Lamprey
Phagocytes,420,471
Pharynx of Amphioxus,410
Phar"nx ofVertebrate,440
Phoronis,439
Phrynus, brain,53
Phry"us,caudal brain,450
Phry"us,carapace and carapace removed,250
Phry"us,cœcal diverticula,109
Phry"us,evidence of segmentation of carapace,249,250,341
Phry"us,operculum,191
Phry"us,prosomatic appendages,306
Phry"us,crossing of dorso-ventral muscles,271,277
Phry"us,stridulating apparatus,368
Phyllodoce,395
Phyllopoda,321
Pigment, in Ammocœtes, in position of atrial cavity,412
Pigm"nt, inepithelial lining of central nervous system,43,457
Pigm"nt, inchoroid of vertebrate eye,104,107
Pigm"nt, inbetween glandular cells round brain of Ammocœtes,211,379
Pigm"nt, intapetal layer of retina,70
Pigm"nt, inwhite, of right pineal eye of Lamprey,76,80
Pineal body,14,15
Pin"aleyes,74,233,244
Pin"al ey"s,of Ammocœtes,80,78,85
Pin"algland,63,75,456
Pits, epithelial, of diaphragms in Ammocœtes,164
Pi"t, epith"lial, ofskin in Ammocœtes,173,200
Pituitary body,244,246,319,321,425,430
Plasma-cells,471
Plakodes,283
Planarians,475
Plastron, formation of cranial walls from the,86,322,341
Plat"ron,of Limulus,136,142,143
Plat"ron,Palæostracan, compared to trabeculæ of Ammocœtes,145,377
Plat"ron,muscles attached to the,270
Plat"ron,of Thelyphonus,143
Platyhelmia,475
Pleuron,410,415
Plexus, of Auerbach,447
Plex"s, ofchoroid,38,45,49,103
Plex"s, ofhypogastric,3
Polychæta,357,395
Pores, abdominal,430
Porifera,473
Pouch, formation of gill,165,166
Prestwichia,24,25,249,351
Principle of concentration and cephalization,51
Prini"ple ofembryology,455
Pristiurus,424
Progress, law of,19
Progr"ss,result of,56
Pronephros,389,397,419,424,449
Prosencephalon,48
Prosoma,52
Protopterus,148
Protostraca,27,396,417
Proto"traca,dominance of,28
Protozoa,166,479
Pseudoniscus,25,249
Pteraspis,29,30,275,326,343,344,350
Pterichthys,29,31,239,326,351
Pterygoid, pedicle of,295
Pterygotus,25,27,56,170,191,221,235,238,249,276
Ptychodera,494,495
Ramus branchialis profundus of facial nerve,311
Ra"mscommunicans,2,3
Raphe,46
Recapitulation, law of,434,456,498
Regeneration of nerves,469
Reptiles, dominance of,21
Retina, compound,71
Ret"ia,development of,101
Ret"ia,inversion of, in Vertebrates,114
Ret"ia,inverted,70
Ret"ia,layers of compound,73
Ret"ia, lay"rs ofin Crustacean eye,100
Ret"ia,of lateral eye of Ammocœtes,93,95,111
Ret"ia,Musca,89
Ret"ia,Pecten and Spondylus,114
Ret"ia,upright compound,72
Ret"ia, upri"htsimple,69
Rhabdites,69,81
Saccus vasculosus,244,322
Scales,345
Scaphaspis,349
Schwann, sheath of,469
Sclerotomes,388
Scorpion, brain,54
Scor"ion,branchial lamellæ,175
Scor"ion,development,482
Scor"ion,entochondrites,377
Scor"ion,excretory organs,397
Scor"ion,eyes,75
Scor"ion,lung-books,150,170
Scor"ion,lymphatic glands,423
Scor"ion,muscles, oblique,278
Scor"ion, mus"les,recti,271
Scor"ion, mus"les,respiration,171
Scor"ion, mus"les,veno-pericardial,177
Scor"ion,muscular system,247,268,269
Scor"ion,nerves to Cheliceræ,237
Scor"ion,olfactory organs,220
Scor"ion,operculum of male,189,206,212
Scor"ion,pecten,359,366,371,373,374,377
Scor"ion,under surface,372
Scor"ion,uterus,189,202,203,204,205,212
Sea-scorpions,25,26,27,56,150,170,191,208,221,232,235,241,349,359
Segmentation, branchiomeric,124
Segmet"ation,body-muscles in vertebrate,388
Segmet"ation,eye-muscles,248
Segmet"ation,of head, double,155,157,173,234,258,411,459
Segmet"ation,of head-shield,339
Segmet"ation,history of cranial,258
Segments, branchial of Ammocœtes,161,178,186
Segm"nts,hyoid, in Ammocœtes, double,186,201,267,300
Segm"nts,innervation of branchial,151
Segm"nts,first mesosomatic, in Limulus and its allies,188
Segm"nts,mesosomatic, of Eurypterus,192
Segm"nts,prosomatic of Limulus and its allies,233,249
Segm"nts, prosm"atic ofAmmocœtes,286
Segm"nts,of spinal region of Vertebrates,388
Segm"nts,of trigeminal nerve-group,257,279
Segm"nts,tubular muscles of hyoid,299
Sense-organs of Amphioxus,34
Sense-o"rans ofbranchial, of Limulus,359,360
Sense-o"rans oflateral, of Annelids,357,367
Sense-o"rans oflateral-line system,356,411,470
Serum,492
Significance of the optic diverticula,102
Silurus,488
Sinus, longitudinal venous, of Limulus,176,312,451
Sin"s,rhomboidal of bird,46
Skeleton, Ammocœtes,126,296,335
Skel"ton, Amm"cœtes,branchial,126,126
Skel"ton, Amm"cœtes,basi-cranial,132
Skel"ton, Amm"cœtes,muco-cartilaginous,291,296,330,331
Skel"ton,aponeurotic,414
Skel"ton,Cephalaspis,414,415
Skel"ton,evidence of the,119
Skel"ton,Limulus, cartilaginous,126,136
Skel"ton, Lim"lus,mesosomatic,137
Skel"ton, Lim"lus,prosomatic,142
Skel"ton,Petromyzon,125
Skel"ton,Vertebrate, commencement of bony,120,121
Skin, digestive power of cells of, in Ammocœtes,58,442
Si"n,of Ammocœtes,346
Si"n,nerves of,448
Skull of dogfish,123
Skl"l ofpig-embryo,121
Slimonia,27,56,170,235,238,249,276,303
Solenocytes,395,477
Solpugidæ,109
Sphæroma serratum, brain,62,90,101,225
Spiders, eyes,75
Spi"ers,stomach,109
Spina bifida,50
Spinal cord, difference between brain and,45
Spi"al cr"d,region of,385
Spi"al cr"d,termination in bird-embryo,51
Spondylus, retina of,114
Squilla, eyes,100
Sqi"lla,glands,422
Stomach, cephalic,4,43,102,244
Stylonurus Lagani,27,235,239,249
Substantia gelatinosa Rolandi,44
Suprarenal body,423
Surfaces, dorsal and ventral,11
Surf"ces,reversal of,15,29,36,87,175,352,433,484
Synapse,72
Syncytium,464,471,479
Tail of lizards,50
Tapetum,69
Teleosteans,23,345,420,424
Tendon-organs,470
Tentacles of Ammocœtes,246,289,303
Tergo-coxal muscles,247
Test, biological, of relationship of animals,492
Thalainencephalon,48
Thelodus,344
Thelyphonus,231
Thely"honus,brain,53,54,56,224
Thely"honus, br"in,caudal,450
Thely"honus,cœcal diverticula,109
Thely"honus,entosternite,143
Thely"honus,genital organs,206
Thely"honus,lyriform organs,368
Thely"honus,olfactory passage,226,306
Thely"honus,operculum,189,190,206,207
Theory, gastræa,444,461
Theories of the origin of vertebrates,9,411,433,457
Thionin reaction,131,139,213,330,336
Throat, formation of,179
Thyestes,30,31,275,326,328,329,339,340,341
Thymus,425,430
Thyroid gland of Ammocœtes,61,127,192,194,196,429,459
Thyr"id gl"ndevidence of the,185
Thyr"id gl"ndfunction of, in Ammocœtes,213
Tissues, connective,471,474,481
Tiss"es,evolution of,19
Tiss"es,notochordal,435
Tiss"es,two groups of,463
Tongue of Ammocœtes,246,303
Tonsils,427,430
Torpedo,262,392,470
Trabeculæ,121,132,133,145,277,295,377