X CONTENTS 



CHAPTER PAGE 



VII. Reproduction and Development 246 



Types of Reproduction 246 



Agamic Reproduction 246 



Gametic Reproduction 250 



Metagenesis 251 



Life Cycle of Moss 252 



Life Cycle of Fern - 255 



Life Cycle of Flowering Plant 255 



Metagenesis in Animals 257 



Ccelenterata in General 258 



The Hydroids 259 



The Scyphozoa 261 



The Actinozoa 261 



Metagenesis in Other Animals 262 



Parthenogenesis 263 



Development 264 



Cleavage 265 



Gastrulation 265 



Gastrulation in the Frog Embryo 267 



Mesoderm Formation 270 



Fate of the Primary Layers 271 



The Neural Tube 271 



The Alimentary Canal 273 



The Visceral Pouches 275 



Nutrition of the Embryo 275 



The Placenta 276 



The Human Embryo and Its Nutrition 277 



Embryonic Membranes 279 



Embryonic Vestigial Structures: Recapitulation 280 



Form and Symmetry in the Developing Embryo 282 



Abnormalities 285 



VIII. Growth, Age, and Death 289 



Age and the Passage of Time 289 



Growth 289 



The Vitamins 292 



Growth and Differentiation 293 



Tumors and Cancers 294 



Regeneration 294 



Rejuvenescence 298 



Duration of Life 300 



