BIOLOGY OF POULTRY KEEPING. IO9 



ing in constitutional vigor, and carrying the determinants of 

 undesirable qualities in their germ cells, the offspring resulting 

 from such a mating will undoubtedly be more nearly worthless 

 than were their parents. If, on the other hand, one inbreeds in 

 the same way strong and vigorous anim^als, high in vitality, and 

 carrying the germinal determiners of desirable qualities there 

 may be expected a corresponding intensification of these quali- 

 ties in the offspring. The time has come wlien a vigorous pro- 

 test should be made against the indiscriminating condemnation 

 of inbreeding. It should be clearly recognized that if the ex- 

 perience of stock breeders extending throughout the world, and 

 as far back as trustworthy data are available, means anything 

 at all it plainly indicates that some degree of inbreeding* is an 

 essential to the attainment of the highest degree of success in 

 the breeding of animals, poultry forming no exception to this 

 rule. 



This contention receives full support from the results of 

 modern exact studies in genetics. Such studies show that the 

 personal bodily characters of the parents have no casual relation 

 to the personal characters of the progeny. What the progeny 

 shall be like is determined by the constitution of the. germ cells 

 of the parents. When by a proper system of selective breeding 

 the point is reached where these germ cells are pure with refer- 

 once to a particular character, or degree of a character, then 

 that character will unfailingly appear in the offspring, in the 

 degree of perfection in which it i^ represented in the germ cells. 

 This is the highest goal of the practical breeder. But in a sex- 

 ually reproducing organism like the domestic fowl purity of the 

 germ cells with respect to the determiners of any character is 

 only to be obtained, in the hands of a practical breeder without 

 special scientific training, by the practice of inbreeding. 



It should not be understood that indiscriminate inbreeding 

 without definite purpose or reason is advised, or advocated as 

 a panacea for all the difficulties which beset the breeder's path. 

 All successful breeding is the working out of carefully made 

 plans. In those plans inbreeding has a place. For the average 



* Of ^course if the term "inbreeding" makes too violent a strain upon 

 anyone's intellectual, moral or merely human prejudices, there is no 

 objection to his using for the practice the term "line-breeding," or some 

 other even milder designation. 



