434 Pork Production 



the fertilized egg, and consequently the new-born pig, is 

 double or dual in nature. In some of his characters the 

 pig may resemble the sire and in others the dam ; in some 

 features he may bear an unmistakable resemblance to an 

 ancestor farther back in his pedigree. Speaking in general 

 terms, it may be said that the hereditary make-up of the 

 pig, his color, set of ear, feeding qualities, vigor, and in 

 fact every character, is the result of the combined heredi- 

 tary influence of his entire ancestry. 



This resemblance between the individual pig and his 

 ancestors is the result of the operation of the law of hered- 

 ity that "like tends to beget like." By this law every 

 living thing reproduces after its own kind and is respon- 

 sible for the faith which the breeder has in the saying 

 "blood will tell." 



Variations. 



Although prepotent breeding animals transmit their 

 likenesses to their offspring with remarkable faithfulness, 

 it is also true that many and wide variations occur among 

 individuals of even identical breeding or ancestry. This is 

 well illustrated by the variations common among the indi- 

 vidual pigs of the same litter, raised together and fed from 

 the same trough. (See Plate XII.) Although heredity 

 impresses or insures a strong family resemblance, it does 

 not operate in a manner to exclude differences or variations. 



Variations among individuals of the same or identical 

 ancestry are of two kinds; first, hereditary variations; 

 and second, variations due to differences in the conditions 

 under which the individuals were developed. 



Hereditary variations among pigs of the same litter are 

 due to differences in the hereditary contents of the germ- 

 cells from which the individuals developed. They are 



