4 8 4 



INDEX. 



Dipnoi, 386 



Dorsal organ, 18, 238 



Double embryos, 281 



Echinoderms, 421 

 larva of, 422 

 Ectoprocta, 443 

 Elasmobranchii, 384 



Endocranium, 16, 20, 306, 312, 319, 436, 450 

 of limulus, 3 14 

 of scorpion, 317 

 summary and comparison, 319 

 of Telyphonus, 319 

 Endoskeleton, 306 

 Enteropneusta, 431 

 Entoprocta, 441 

 Epibranchial organs, 17 

 Epiphysis, 133, 136 

 Equilibrium, 191 



Evolution of bilateral symmetry, 457 

 cosmic, 454 



of creative environment, 454 

 crices in, 456 

 of metamerism, 457 

 of social environment, 454 

 Eye, ectoparietal, 134 



environment of lateral, 462 

 endoparietal, 134 

 frontal, 125 

 lateral, 127, 149 

 ganglia, 154 

 lens, 151, 153 

 parietal, 125, 126, 129 

 of apus, 138 

 of branchipus, 136 

 of limulus, 131 

 of scorpion, 129 

 of vertebrates, 139 

 of ganglia, 142 

 lens of, 144 

 placodes, 146 

 tube, 133, 136 



Fiber cells, 232 

 Fins, pectoral, 251 



pelvic, 251 

 Fission, longitudinal, 282 



transverse, 282 

 Flabellum, 94, 113 

 Flexure cranial, 65 



forebrain, 55 



hind-brain, 69 

 Fringing processes, 269 

 Frontal eye, 125 



organs, 165 

 Fusiform cells, 447 



Ganglia, cardiac, 202 



of cord, 97 



cranial, 17, 81, 95 



habenulse, 142 



lateral eye, 155 



pedal, 81, 95 



optic, 62, 154 



stomodaeal, 15, 60 

 Gaskell, 34 

 Gastrula, 34, 404, 433 



in limulus, 227 

 Gastrulation, 248 



Germ disc, 224 



layers, 229 



wall > 23, 35, 228, 237 

 concrescence of, 35 

 Gill arches, 261 



external, 261 



pouches, 251 



sacs, 263 

 Growth, apical, 246 



causes of differential, 215 



interpretation of early stages of, 219 

 Gustatory apparatus, 186 



nerves, 84 

 roots, 84 



organs, in 



tracts, 84 

 Gut pouches, 266 



Haemal, nerve cord, 43' 

 roots, 77, 8 r 



surface, orientation of, 27, 221 



tracts, 85 



Hasmostoma, 25, 40 

 Head cavities, 23 



subdivisions of vertebrates, n 

 Heart, 39 



beat, 207 



cardiac ganglia, 200, 202 



cardiac nerves, 200 



comparison of vertebrate and arachnid, 197 



development of, 195 



experiments on, 205 



lateral cardiacs, 200 



location of, 195 



pericardial nerves of, 200 



segmental cardiacs, 200 

 Hemisphere association cells, 58 



development of, 55 

 Herrick, 34 

 Holocephali, 385 

 Hydrocele, 426 

 Hypophysis, 260 



Infundibulum, 18, 62 

 Jaws, 250, 255-257 



Lateral eye of vertebrates, 151 

 ganglion, 154 



fold, 269 



line organs, 121 



plates of mesoderm, 22 

 Leg jaws, 15, 250 

 Lemmatochord, 323 



of lepedoptera, 326 



of limulus, 334 



of scorpion, 329 

 Lens, parietal eye, 144 

 Lernasa, branchiata, 408 

 Limnadia lenticularis, 409 

 Lobes olfactory, 13 



procephalic, 38 

 Lobi inferiores, 18-62 

 Locomotor appendages, 268 

 Locomotion, 191 



Macrocystis, 301 

 Marine arachnids, 337 

 origin of, 338 



