FARM ANIMALS. ;3<>5 



IV. Variation 



may be defined as the tendency in animals to 

 produce characters in the offspring which differ 

 from those of the parents. This law has given 

 rise to the common expression that " like does 

 not always produce like." At first sight these 

 two principles would appear antagonistic ; but 

 upon further study their difference may be 

 understood. 



As the result of reproduction of animals of a 

 certain breed, we expect offspring which re- 

 semble the parents in general breed characters. 

 For example, it is natural to expect an Aberdeen 

 Angus cow to be the mother of a hornless calf, 

 black in color and of meat-producing confor- 

 mation ; and we will not expect her to be the 

 mother of a fawn-colored calf with horns and 

 capable of milk production at maturity rather 

 than beef production. Thus, within limits, 

 " like produces like." On the other hand, we 

 would not expect this calf to be exactly like its 

 mother in every respect, for who has ever seen 

 two animals or two people exactly alike ? The 

 calf might differ from its mother in size, spring 

 of ribs, thickness of loin, length of legs, depth 

 of bod)' and various other ways. Thus, we see 

 that like does not always produce like. Should 

 the calf differ from its mother in these minor 

 details, this variation would be called gradual or 

 ordinary variation. But should it possess some 



