VALUE OF IMPROVED BREEDS 403 



is inherited or merely the ability to be trained. In view 

 of the last two examples, the latter seems much the more 

 probable. The effects of continued selective breeding are, 

 therefore, to be ascribed to the gradual accumulation of 

 numerous genes all of which contribute something toward 

 speed. 



The Value of Improved Breeds is out of all propor- 

 tion to the cost of producing them. It costs little or no 

 more to feed a thoroughbred than a scrub cow, but 

 the quantity of milk and butter received may in ex- 

 treme cases be ten times as great. It is certainly the 

 duty, therefore, of individuals and governments to pro- 

 mote the breeding of superior stock, not only of dairy 

 cattle and fowls but of many other domesticated animals; 

 for what is true of milk, butter, and eggs is also true in 

 general terms for beef, pork, and mutton, wool, hides, and 

 silk. 



Summary. — The practical animal breeder has car- 

 ried many species and varieties to a high state of perfec- 

 tion. Where the knowledge of the genes involved is 

 sufficient, they appear to behave in the same man- 

 ner as those with which we are acquainted in the 

 experiment garden and breeding pen. The methods 

 employed are either continued selection in a variety 

 toward an ideal, or selection after hybridization. The re- 

 sults of selection in both cases appear to be best explained 

 on the assumption of the gradual assembling of many 

 favorable genes in a more or less pure genotype. The 

 genes are probably so numerous that no " pure race " has 

 yet reached a point where it is pure for every pair of 

 genes. Consequently, it may be confidently hoped that 

 continued breeding will improve even the best of breeds. 



