CONTENTS xiii 



CHAPTER PAGE 



Supporting Structures ...... 123 



Circulatory System . . . . . . .126 



Alimentary System . 126 



VI. ONTOGENESIS 129 



Biogenesis and Abiogenesis 130 



Reproduction as a Growth Process .... 131 



Fission in Metazoa . . . . . . .132 



Fission in Lower Plants 135 



Temporary Budding 136 



Permanent Budding ...... 139 



Spore Formation ....... 140 



Sexual Reproduction 141 



Total Conjugation 142 



Isogamy . . . . . . . . 142 



Anisogamy 144 



Sexual Differentiation ..... 147 



Partial Conjugation ...... 151 



Cytoplasmic Conjugation (Plastogamy) . . 151 



Nuclear Conjugation (Karyogamy) . . .152 



Nuclear Phenomena of Zygosis in Animals . .155 



Cleavage 158 



Gastrulation 161 



Further Differentiation 162 



Conjugation in Protozoa 164 



Parthenogenesis . . . . . .167 



Artificial Parthenogenesis . . . . .169 



Alternation of Generations in Animals . . 171 

 Sexual Reproduction in Plants . . . .174 



Liverworts and Mosses .... 175 



Ferns 176 



Seed Plants . . . . . . .177 



Germination of the Megaspore . . .179 



Germination of the Microspore . . .179 



Parthenogenesis in Plants . . . .182 



Apogamy ....... 183 



The Probable Evolution of the Plant World . . 183 



Morphogenesis . . , , . . .185 



Regeneration ........ 185 



