692 



INVERTEBKATA 



Ventral cell-family in segmenting egg of 



Ascaris megalocephala, 440 

 Ventral ciliated epaulettes, formation of, in 



larva of Echinus esculentus, 511 

 Ventral ganglion, formation of, in Sayitta 



bipunctata, 432 

 Ventral nerve-cord, formation of, in Orio- 



drilus lacuum, 158 ; in Nephelis, 162 ; in 



Peripatus capensis, 174 ; in Polygordius 



appendiculatus, 147 

 Ventral organs, formation of, in Peripatus 



capensis, 174 

 Ventral plate in the embryo ofAgelena, 224 ; 



in embryo of Unio, 351 

 Ventral retractor muscles, formation of, in 



larva of Dreissensia, 341 

 Ventral shield in embryo of Astacus, 186 

 Ventral sinus, formation of, in Nephclis, 163 

 Ventricle of heart, formation of, in Cyclas, 



350 ; in Loligo, 362 

 Ventro-lateral chamber of Urticina crassi- 



cornis, 80 

 Vertebra, formation of, in Amphiura squa- 



mata, 499 

 Vertebrata, 29, 162, 568, 569, 584, 585, 



586, 605, 606, 608, 625, 636, 646, 662 

 Vesicula seminalis of Ascaris megalocephala, 



438 

 Vestibule, formation of, in larva of Antedon 



rosacea, 557 ; in larva of Pedicellina, 400 

 Vibratile cleft, formation of, in Cyphonautes 



larva, 390 

 Vibratile plume, formation of,iii Cyphonautes 



larva, 391 

 Visceral ganglion, formation of, in larva of 



simple Ascidian, 622 ; in Dreissensia, 



342 ; in Loligo, 358 ; in Paludina, 315 

 Visceral hump, formation of, in Loligo, 



361 ; in Patella, 300 

 Visceral muscles, formation of, in Oriodrilus, 



158 ; in Donacia, 256 ; in Polygordius 



appendiculatus, 147 

 Visual rods, of Cephalopod eye, formation 



of, 368 ; of ocelli of Dytiscus, 273, 274 

 Vitellarium of Callidina russeola, 424 

 Vitelligenous- cells of Platyhelminthes, 102 

 Vitelliue membrane, definition of, 3 ; forma- 

 tion of, 9, 17 ; in egg of Amphioxus, 



587 ; in unfertilized eggs of Echinoidea, 



524 

 Volvox, 660 ; compared with blastula, 51 



Water-tubes of larva of Asterias, 466 



Water-vascular system of Echinodermata, 

 see Hydrocoele 



Wheel-organ, formation of, in Amphioxus 

 lanceolatus, 604 ; in Callidina russeola, 426 



Wheels in larva of Synapta diyitata, 535 



White bodies, formation of, in Loligo, 361 



Wings of Doryphora, development of, 271, 

 273 



V\ ings, rudiments of, in larva of Galerucella 

 ulmi, 268 



Wing-sac of Buprestidae, 277 ; of Ceram- 

 bycidae, 277 ; of Culicidae, 278 ; in 

 Doryphora, 271 ; in Insecta, various types 

 of, 277-279 ; of Lepidoptera, 278 ; of 

 Muscidae, 278, 279 ; of Scarabaeidae, 

 277 ; of Tipulidae, 278 



Worm-like larva of Ophiura brevispina, 562 



Xiphosura, 221 



Yoldia, larva of, 349, 369 



Yolk, influence of, on segmentation of egg, and 



on the formation of layers in the embryo, 



26, 657 

 Yolk -cells, formation of, in embryo of 



Donacia, 247 ; in embryo of Lepisma, 



264 ; in embryo of Pyrosoma, 633 ; in 



Scolopendra, 282 

 Yolk-lobe in egg of Dentalium, 326. (See 



also Polar lobe.) 

 Yolk-membrane, formation of, in egg of 



Sepia, 3S5 

 Yolk-nucleus, definition of, 3 ; of egg of 



Cynthia partita, 610 

 Yolk-sac, development of, in Helix, 369 ; 



in Loligo, 360 

 Yungia, 161 ; development of larva of, 112- 



115 



Zoaea larva, 217 ; description of, 208 ; in- 

 terpretation of, 210-212; of Auomura, 

 210, 213 ; of Brachyura, 210, 213 ; of 

 Caridea, 209, 213 ; of Euphausidacea, 

 208, 212 ; of Penaeidea, 209, 212 



Zoantharia, 53 ; development of, 76-86 



Zoanthella larva of Zoanthidae, 85 



Zoanthidae, 53 ; larvae of, 85 



Zoanthina larva of Cereanthidae, 85 



Zooecium, formation of, in Polyzoa Erto- 

 procta, 396, 397 



Zygonema, definition of, 4 



Zygote, definition of, 2 



Zygote nucleus, definition of, 9 



Zygotene thread, definition of, 4 



END OF VOL. I 



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