6 CONTENTS. 



PAGE 



In-and-in breeding: — Used for fixing characters — Evil 

 effects of. 



Prepotency : — Defined — Males usually prepotent — 

 Chamoise sheep. 



Growth. 



CHAPTER II. 

 Theories of Heredity and Variation .48 



Heredity is self-evident — Variation demands explan- 

 ation — Variation defined as applying to characters — Con- 

 genital and acquired characters — Variations existing at 

 birth are congenital. 



Assigned causes of congenital variation: — Climate and 

 environment — Ancestral use and disuse — Unlike parents — 

 Views of Aristotle — Inherited mutilations — Lamarck's 

 laws. 



Weismann's theory: — Cells — Multiplication of cells — 

 Conjunction of cells — Germ cells and somatic cells — Pro- 

 pagation by conjunction of cells — Continuity of the germ 

 plasm — Germ cells protected from exterior influences — Neo- 

 Darwinians and neo-Lamarckians — Conflict between their 

 theories — Practical necessity of knowledge on the subject. 



CHAPTER I'll. 

 Basis of Investigation 59 



The problem stated — Non-functional characters — Func- 

 tionally active organs — Organs compared — Effect of func- 

 tional activity — Functional capacity — Use-inheritance 

 means the inheritance of acquired functional capacity — 

 The brain as a functional organ selected for investigation. 



Deduction from Weismann's theory: — Law of proba- 

 bilities — Extent of variation — Relative fertility of classes — 

 Result of different degrees of fertility — Present condi- 

 tions show that the lower classes produce more rapidly than 



