TABLE OF CONTENTS xiii 



CHAPTER VllI 



Reproduction 165 



Spontaneous generation — Experiments discrediting spontaneous generation 

 — Modern idea of spontaneous generation — Reproduction — Asexual repro- 

 duction: budding — Internal budding — Fission — Sporulation — Limits of 

 asexual reproduction — Sexual reproduction — Sexual reproduction in metazoa 

 — Sexual reproduction in Protozoa — Possible maturation in Protozoa — 

 Significance of fertilization in Protozoa — Parthenogenesis — Paedogenesis — 

 Hermaphroditism — Combined types of reproduction — Artificial partheno- 

 genesis — Nature of fertilization — References. 



CHAPTER IX 



The Breeding Habits of Animals 189 



Methods of insuring fertilization — Fertilization in hermaphroditic animals — 

 Fertilization ia dioecious species — Summary of methods of fertilization — Do 

 the methods of insuring fertilization exhibit an evolutionary series? — Place 

 of development — Source of nourishment of the embryo — Summary of locus 

 and nutrition of the embryo — Oviparity — Viviparity — No evolutionary 

 sequence — Care of fertilized eggs — Care of young after birth or hatching: 

 birth stages — Relation of birth stages to parental care — Conclusion. 



CHAPTER X 



li^MBRYOLOGY 206 



Early origin of germ cells — Origin of germ cells in the invertebrates — Origin 

 of germ cells in the vertebrates — Maturation — Spermatogenesis — Tetrads — 

 First maturation division — Second maturation division — Oogenesis — Tetrads 

 — First maturation division — Second maturation division — Comparison of 

 maturation in male and female — The eggs — The spermatozoa — Fertilization 

 — Cleavage — Cleavage in homolecithal eggs — Cleavage in telolecithal eggs 

 — Cleavage in centrolecithal eggs — Gastrulation — Gastrulation in homolec- 

 ithal embryos — Gastrulation in telolecithal embryos — Mesoderm formation 

 — Organogeny in the vertebrates — The early embryo — Digestive tract and 

 its derivatives — Gill pouches — Mouth — Liver — Pancreas — Lungs — Minor 

 features of digestive tract — Central nervous system — The nerves — The eye 

 — The ear — Olfactory organ — Metamorphosis — Metamorphosis in inverte- 

 brates — Metamorphosis in vertebrates — Homology — Origin of homology — 

 Biogenetic law — Mechanism of development — Explanations — Independence 

 of the germ cells — Immortality of germ cells — Germ cells, a reserve supply — 

 References. 



/ CHAPTER XI 



Genetics 239 



Scope of genetics — The genes or factors — Terminology — Color in guinea pigs 

 — Explanation of the experimental results — The Fs generation — Accuracy of 

 the ratios — Simultaneous inheritance of two pairs of characters — Linkage 

 " — Gregor Mendel — Mendel's law — Determination of sex — Sex linkage — 

 Mechanism of heredity: a retrospect — Definition of heredity — Variation — 

 Genetics and evolution — Genetics and race — Practical applications of genetics 

 — References. 



