LINE BREEDING. 107 



continuous in-and-in breeding. On the heels 

 of that expiring system followed a practice 

 which some of its exponents sought to distinc- 

 tively designate as inbreeding, but this term 

 was not sufficiently differentiated from in-and- 

 in breeding (perhaps the practice described by 

 the two terms were none too separable to the 

 vulgar eye) to be generally understood as a 

 different practice, and these men, as they grew 

 more and more away from any general practice 

 of incestuous breeding, took up the term line 

 breeding as designating their method. The 

 actual affinities of "line breeding" are beyond 

 the power of human ingenuity to discover. 

 The process of defining the term has been a 

 perfect "open-entry," "go-as-you-please" con- 

 test, in which many have taken a part and 

 nearly all have desired an exclusive liberty of 

 action, ruling off all competitors. The reason 

 of this is not far to seek. 



Beginning with any given pair of animals if 

 their produce be interbred and their produce 

 again, and the progeny should be numerous, 

 then after the third generation the crosses 

 would cease to be incestuous, but would con- 

 tinue to be "line bred." Now this is exactly 

 analogous to the case of the Jews, in which 

 in-and-in breeding early gave way to line- 

 breeding of this sort. As I understand the pro- 

 cess, this is, properly and logically speaking, the 



