xviii CONTENTS 



PAGE 



The soma and germ plasm experimental investigations 485 



The isolation of the germ plasm 488 



The inadequacy of affirmative evidence 489 



The transmission of functional modifications 491 



Parallel induction 492 



The adequacy of other factors 493 



The conclusion 494 



CHAPTER XXXI 

 THE SELECTION PROBLEM IN ANIMAL BREEDING 



Introductory 495 



General views of selection 495 



The American standard bred horse 495 



Fecundity in fowls 497 



Bantam fowls 499 



Selection and breeding methods 500 



Selection indices 502 



CHAPTER XXXII 

 HYBRIDIZATION IN ANIMAL BREEDING 



Introductory 508 



Growing importance of hybridization 508 



Grading 508 



Crossbreeding 514 



Species hybridization among domestic animals 515 



CHAPTER XXXIII 



DISEASE AND RELATED PHENOMENA IN ANIMAL BREEDING 



Introductory 522 



The inheritance of disease 522 



The inheritance of predisposition to disease 523 



The inheritance of defects 524 



Defects in domestic animals 526 



Immunity to disease 527 



Breeding for immunity . . . . '. 529 



CHAPTER XXXIV 

 SEX IN ANIMALS 



Introductory 536 



The determination of sex 536 



Sex-determination in mammals 536 



Sex-determination in birds 539 



The sex-ratio 539 



