LIST OF ILLUSTRATIONS xxi 



FIG. PAGE 



54. Bougainvillea ramosa 235 



55. Diagrams illustrating derivation of Medtisa from Hydranth . 238 



56. Eucopella campanularia, muscle-fibres and nerve-cells . . . 242 



57. Laomedeaf.exuosa^\\^.Eudendriumrainosum, development. 246 



58. Diphyes campanulata 248 



59. For pita pacifica and P. mediterranea 250 



60. Spermatogenesis in the Rat . 253 



6 1. Ovum of Toxopneustes lividus 255 



62. Maturation and impregnation of the animal ovum .... 256 



63. The gastrula ... 261 



64. JHagosphczra platiula . . 262 



65. Volvox globator 263 



66. Diagram illustrating the hypothetical origin of the gastrula 



from a colony of unicellular zooids 264 



67. Diagram illustrating the hypothetical origin of the gastrula 



from a solitary multinucleate form 265 



68. Polygordius neapolitanus, external form . 268 



69. Polygordius neapolitanus, anatomy .... .... 270 



70. Polygordius neapolitamis, nephridium 281 



71. Polygordius, diagram illustrating the relations of the nervous 



system 283 



72. Polygordius neapolitanus ', reproductive organs 290 



73. Polygordius neapolitanus, larva in the trochosphere stage . . 292 



74. Diagram illustrating the origin of the trochosphere from the 



gastrula 294 



75. Polygordius neapolitanus, advanced trochosphere .... 296 



76. Polygordiiis neapolitanus, larva in a stage intermediate be- 



tween the trochosphere and the adult .... . 299 



77. Starfish, diagrammatic sections .... . . 36 



78. Crayfish, diagrammatic sections . 3 12 



79. Mussel, diagrammatic sections . 3 X 7 



80. Dogfish, diagrammatic sections 3 22 



81. Mosses, various genera, anatomy and histology 329 



82. Funaria, reproduction and development . . . 334 



83. Pteris and Aspidium, anatomy and histology . 34 2 



