SYSTEMS OF BREEDING 617 



from close breeding, or is it merely that vigor and fertility are 

 commonly defective characters and frequently find themselves 

 on the losing side ? Undoubtedly it is the latter. There are 

 cases enough of the greatest vigor and fertility of inbred indi- 

 viduals, and of family lines and even of whole species, to set 

 aside all fear of inevitable injury from close breeding, but a 

 little study will convince us that there is lurking weakness and 

 infertility everywhere. It is said that one third of our children 

 die in infancy. A large proportion of animals and an apparently 

 larger proportion of plants are relatively weak and easily suc- 

 cumb to disease or to the encroachments of their neighbors. 



Few individuals are fully fertile, that is, free and regular 

 breeders, and fewer yet are both fertile and vigorous. Short- 

 comings in these two respects may be called the distinguishing 

 defects of both plants and animals under domestication. In 

 nature they constitute the chief points of attack of natural selec- 

 tion, but in domesticated animals and plants we commonly select 

 for other points, even color, trusting to luck for vigor and fertility. 

 Is it any wonder that these lurking evils have crept upon us 

 until they often constitute an insurmountable bar to inbreeding, 

 and have invaded even our most carefully outbred herds ? 



As inbreeding is the supreme test of a race, so it is of a char- 

 acter ; if a character suffers by inbreeding it is a sign of natural 

 defectiveness and should be accepted as such, and not laid up 

 as an additional instance and a weapon with which to abuse a 

 system with a history of laudable achievement in the past and 

 rich with possibilities for the future. 



When we select for vigor and fertility we shall hear less of the 

 evils of inbreeding. In the meantime we shall hear most about 

 it where vitality and fertility are naturally lowest. Both are 

 cardinal requisites, one for life, the other for reproduction, 

 and both must be possessed in a high degree by any individual 

 or family line that is to figure much in descent. 



Noting, then, the remarkable instances of successful inbreed- 

 ing, as well as its unexampled capacity for trouble, we arrive 

 at the conclusion that the disaster from inbreeding is probable, 

 but not inevitable. With that much gained, it is worth while to 

 examine further into this disputed territory. 



