CONTENTS 
Causes of unusual sex-ratios . a 
Metabolic theories of sex-determination . 
Inheritance of unusual sex-ratios . 
Secondary sexual characters . 
The effects of castration . 
CHAPTER XXXV 
Frertiviry in ANIMALS 
Introductory . 
Factors influencing fertility, 
The Darwinian theory of fertility. 
Inbreeding not in itself harmful 
Fertility as related to Mendelian factors. 
The chromosomes and fertility—Drosophila . 
Sterility in other animals 
Sterility in hybrids . : 
Fertility as related to hel MaOre ; 
Fecundity in fowls . 
Conclusion 
CHAPTER XXXVI 
Some Briers or PracticaL BREEDERS 
Introductory 
Telegony 
Harmful effects a ora eatiar 7 
Infection of the male. Saturation 
Maternal impression 
Prepotency : 
The Mendelian Palerpretation 
The relative factor interpretation . 
The hereditary complex interpretation 
Greater prepotency in the male 
Conclusions . 
CHAPTER XXXVII 
MertuHops or BREEDING 
Introductory . . 
Methods means [o an atl 
Phenotypic selection : 
Limitations of ena rier en : 
Pedigree breeding : 
Breeding systems based on blood piatonehin 
Inbreeding. 
Line breeding 
Out-breeding. : 
Other systems of breeaine : 
Genotypic selection . 
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