CHAPTER XXXI 

 THE SELECTION PROBLEM IN ANIMAL BREEDING 



There are two general views respecting the effectiveness of selection, 

 namely, that it depends upon the isolation of hereditary material of the 

 most excellent kind, or in metaphor that selection separates the gold 

 from the dross, and secondly that it is due to modification of germinal 

 elements, that by selecting in a specific direction the hereditary material 

 itself is actually molded in a corresponding fashion. The two inter- 

 pretations are fundamentally at variance each with the other; one 

 interpretation would have it that the hereditary elements are relatively 

 constant, at least that they are not subject to gradual continuous change; 

 the other interpretation favors a belief in factor inconstancy, insignificant 

 fluctuating variability as it were in factors themselves, which provides 

 opportunity by appropriate selection for actual modification of germinal 

 elements. These opposed views have already been discussed at some 

 length in other chapters, it remains to apply the conclusions therein 

 reached to practical animal breeding operations; and to discuss certain 

 other phases of the selection problem which are of particular interest 

 in practical work. 



In spite of vigorous statements to the contrary, there seems to be 

 little reason to doubt that the isolation view of selection can account for 

 all results which have been communicated thus far with respect to this 

 question, whether of practical experience or of experimental research. 

 In the preceding chapter we had occasion to consider, in passing, the 

 reduction which had occurred in trotting records during the past one 

 hundred years. Data of this kind are not lacking in the annals of agri- 

 culture, and are often offered as evidence in support of the belief in the 

 gradual accumulation of favorable increments in the development of 

 breeds. But although this old Darwinian idea of improvement in animals 

 is very generally subscribed to, at least verbally, by practical men, it 

 is nevertheless true that whenever a critical examination is made of 

 specific instances the support for it largely disappears. 



The American Standard Bred Horse. In Table LXIII are given the 

 data which indicate how the trotting record has been lowered during 

 the history of racing in America. A parallel table might be given to 

 show how the pacing record has been reduced. Now although these 

 records have been used on the one hand in support of belief in the inheri- 



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