20 MAINE AGRICULTURAL EXPERIMENT STATION. I917. 



with reference to all important characters or ciualities. The 

 quickest way, indeed the only way, practically to obtain this 

 result is by the practice of some degree of inbreeding. Some- 

 times a great stride towards the desired end may be made by 

 mating brother and sister or parent and offspring together. 



That a mating of such close relatives will surely result in 

 disaster is one of the carefully nursed superstitions of breed- 

 ing, which has often been exploded, but will doubtless always 

 be with us. It may be said that all the evidence which may 

 be gleaned from the experience of stock breeders indicates 

 that the results which follow inbreeding depend entirely upon 

 the nature of the individuals inbred. If one inbreeds weak 

 animals, lacking in constitutional vigor, and carrying the deter- 

 minants of undesirable qualities in their germ cells, the o'fif- 

 spring resulting from such a mating will undoubtedly be more 

 nearly worthless than w^ere their parents. If, on the other 

 hand, one inbreeds in the same way strong and vigorous ani- 

 mals, high in vitality, and carrying" the germinal determiners 

 of desirable qualities there may be expected a corresponding 

 intensification of these qualities in the offspring. The time 

 has come when a vigorous protest should be made against the 

 indiscriminating condemnation of inbreeding. It should be 

 clearly recognized that if the experience of stock breeders ex- 

 tending throughout the world, and as far back as trustworthy 

 data are available, means anything at all it plainly indicates 

 that some degree of narrow breeding is an essential to the 

 attainment of the highest degree of success in the breeding of 

 animals. 



This contention receives full support from the results ot 

 modern exact studies in genetics Such studies show that the 

 personal bodily characters of the parents have no causal rela- 

 tion to the personal characters of the progeny. What the pro- 

 geny 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 reference to a particular character, or degree of a char- 

 acter, then that character will unfailingly appear in the off- 

 spring, in the degree of perfection in which it is represetned 



