294 THE BREEDING OF ANIMALS 



the sense that they have been selected to a point where 

 the germ-plasm of different individuals of the breed, is 

 identical in composition. The pure line of the biologist 

 is after all a purely imaginary conception. It is conceiv- 

 able that such a condition may be produced among self- 

 fertilizing plants, but among the higher animals it is 

 certainly true that no such germinal purity has yet been 

 attained. The practical animal-breeder may still con- 

 tinue to hold fast to selection as his chief means of im- 

 provement with the assurance that in all the higher do- 

 mestic animals we have not yet reached the ultimate 

 limits of improvement. The animal-breeder has not 

 yet produced a pure line, biologically speaking, and has 

 not, therefore, reached a point in his breeding when it 

 can be accurately said that selection is without effect. 1 



279. Pedigree. The pedigree of an animal is a record 

 of the ancestors. It is a valuable historical document. 

 If it includes the names of many animals of outstanding 

 quality, it is a good pedigree. If the ancestors were 

 mediocre individuals of no special merit, the pedigree 

 is inferior. The mere fact that an animal is recorded in 

 a recognized herd-book does not signify that such animal 

 has a good pedigree. The careful breeder must have a 

 thorough knowledge of the history of the breed and espe- 

 cially of the ancestors of the individual animal under 

 examination. 



The immediate ancestors are most important. A 

 noted sire or dam appearing in the pedigree six or eight 

 generations back is of far less importance than one which 

 appears in the first, second or third generations. Many 

 breeding animals are sold on the strength of the fact 



Castle, "Pure Lines and Selection," Journal of Heredity, 

 1914, p. 93. 



