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 



