LIST OF FIGURES xix 



FIG. PAGE 



8 1. Ovarian eggs of Limulus and Polyzonium . . . .159 



82. Formation of the spermatozoon in A nasa . .162 



83. Transformation of the spermatids of the salamander . . . . .164 



84. Formation of the spermatozoon in Salamandra and Amphiuma . . . .166 



85. The same in Helix and in elasmobranchs . . . . . . , .168 



86. The same in mammals . . . . , .169 



87. Formation of spermatozoids in cycads . . . t . .173 



88. Formation of spermatozoids in cryptogams . . . , . . 174 



CHAPTER IV 



89. Fertilization of Physa . . . . . . . . . . .180 



90. Fertilization of Ascaris . . . , . . . . . . .183 



91. Germ-nuclei of Nematodes .,.. 184 



92. Fertilization of the mouse 185 



93. Fertilization of Pterotrachea . . . . . . . . . 1 86 



94. Entrance and rotation of sperm-head in Toxopneustes . . . . . .187 



95. Conjugation of the germ-nuclei in Toxopneustes .,,..... 189 



96. Diagrams of fertilization 190 



97. Fertilization of Nereis . . , . .191 



98. P'ertilization of Cyclops 193 



99. Fertilization and persistence of centrosomes in Thalassema . . . .195 



100. Entrance of spermatozoon into the egg , , , . . . . . 197 



101. Pathological polyspermy ... . . . . . . 199 



102. Polar rings of Clepsine . . . . . . . . . .201 



103. Paths of the germ-nuclei in Toxopneustes ..... 203 



104. Fertilization of Myzostoma , , 209 



105. Fertilization of Pilularia . . . . . . . . . . . 216 



106. Penetration of the pollen-tube in angiosperms 217 



107. Fertilization of the lily 219 



1 08. Fertilization in Zamia ........... 220 



109. Diagram of conjugation in Infusoria . . . . . . . 223 



110. Conjugation of Paramcecium ...... o .<,. 225 



111. Conjugation of Vorticella 226 



112. Conjugation of Noctiluca ... ........ 227 



113. Conjugation of Spirogyra ...,.., -. . . 228 



CHAPTER V 



1 14. Polar bodies in Toxopneustes 234 



115. Genesis of the egg c 235 



1 1 6. Diagram of formation of polar bodies . . . . . .237 



117. Polar bodies in Ascaris 239 



1 1 8. Genesis of the spermatozoon c 240 



119. Diagram of reduction in the male . 242 



1 20. Spermatogenesis of Ascaris . . 244 



121. Diagrams illustrating tetrad-formation . . . o o 247 



122. Tetrads of Gryllotalpa ....'.,.. o <.. 249 



123. Tetrads and polar bodies in Cyclops ......<>.. 250 



