! 36 VARIATION 



species has thrown off its albino variety, which in most cases is 

 easily propagated. Hornless cattle occasionally appear in nearly 

 all breeds, and the type is comparatively easy of preservation. 

 It is more than likely that the different types in the larger 

 breeds, which breeders find so difficult to break up, are in 

 reality quite distinct. 



In future chapters dealing with the measurements of variation 

 and the statistics of heredity in general, it will appear that even 

 fixed types afford sufficient deviation to keep a breeder busy 

 with selection ; in other words, that the animal breeder dealing, 

 as he is, with small numbers will always find sufficient variation 

 to lead him to suppose that he is getting results of his selection 

 even when he has not shifted the center of variation the slight- 

 est. Much that passes for breeding is nothing more than this 

 ineffectual multiplication, and it is not too much to say that 

 hundreds of breeders and thousands of animals have lived and 

 died without affecting the breed in the slightest. 



The writer is strongly of the opinion that while selection is a 

 powerful agent for " shaping up " and " finishing off " a fairly 

 acceptable type, and while it is the only means of deciding 

 what shall live and what shall disappear, yet much of the real 

 advance in both animal and plant breeding is likely to come 

 through distinct offsets which are now called mutations, and 

 which in Darwin's time and until recently were erroneously, if 

 not reproachfully, denominated " sports." 



SECTION VI BIOLOGICAL SIGNIFICANCE OF 

 MUTATIONS 



Too much mystery has surrounded this matter of sports, 

 and there has been a too ready tendency to evoke the aid of 

 latent characters to explain this and almost every other unusual 

 phase of evolution. 



In truth, there is no more mystery about mutations than 

 about heredity in general, which is a complication of mysteries. 

 It is not a question of latency but of relative prominence of 

 characters, of the possible loss of a racial peculiarity, or, what 



