LIST OF ILLUSTRATIONS 



FIG. 



55- 

 56. 

 57- 

 58. 

 59- 

 60. 

 61. 

 62. 



63- 

 64. 



65. 

 66. 

 67. 

 68. 

 69. 



70. 



71- 

 72. 



73- 

 74. 



75- 

 76. 



77 



7' 

 7 



Diagrams illustrating derivation oi Medusa and Hydrant h . 241 



Eucopelia cavipaniilaria, muscle fibres and cells 243 



Laomedeajlexuosa and Eiidendrium ramosttm, development. 247 



Diphyes catnpaimlata 250 



Porpila pacifica and P. mediterranea 251 



Spermatogenesis in the Mole-cricket 254 



Ovum of Toxopneusles lividus 257 



Maturation and impregnation of the animal ovum .... 258 



Pandorina mortim 263 



Volvox globator • 265 



Volvox globator 266 



Polygordius tteapolitaitus, external form 269 



Polygordius neapolitanus, anatomy 271 



Polygordius iieapolitanus, nephridium 282 



Polygordius, diagram illustrating the relations of the nervous- 

 system 284 



Polygordius neapolitanus, reproductive organs 291 



Polygordius neapolitanus, larva in the trochosphere stage 293 

 Diagram illustrating the origin of the trochosphere from the 



gastrula 295 



Polygordius neapolitanus, advanced trochosphere 297 



Syiygordius neapolitanus, larva in a stage intermediate be- 

 tween the trochosphere and the adult 300 



tarfish, ventral aspect 307 



tarfish, diagrammatic sections 309 



tarfish, digestive organs 311 



tarfish, water vascular system 313 



Itarfish, early stages in development 316 



Itarfish, development of bipinnaria larva 317 



!rayfish, side view 319 



Irayfish, principal appendages 322 



Irayfish, diagrammatic sections 328 



!rayfish, action of abdominal muscles 330 



Irayfish, leg, with muscles 331 



!rayfish, dissection 333 



