ANIMAL BREEDING 657 



If, now, to this we add, say, three other requirements ("points") 

 represented respectively by J-, J^, and ^, we have reduced our 

 chances to \ x ^ X T ^ X \ X ^ X ^, or 1 1 5,200, meaning 

 that not one individual in 100,000 will meet our demands. But 

 this is beyond the range of practical selection, and it means that 

 defects will of necessity be accepted. If the same defect were 

 always accepted the damage would be less, but in practice one 

 point is now waived and then another, as we choose the least 

 of two evils, and so defects linger and, behaving according to 

 the principles of Mendel's law, return to plague us long after 

 we supposed ourselves through with them and well freed from 

 their influence. This is really mixed breeding, however pure 

 the pedigree. 



Now the principle is this : we should tolerate no more points 

 at any one time than can all be found in the same individuals. 

 When the entire population come to possess these few charac- 

 ters in a high degree, then other requirements can be safely 

 added, because the breeding for a few characters at a time 

 amounts to practical certainty. The breeds with which this 

 method has been practiced racing horses and hunting dogs, 

 for example have outstripped anything known in the rapidity 

 of their improvement, and, moreover, a foundation has been se- 

 cured on which other requirements may safely be laid ; whereas 

 the breeds in which many requirements have been exacted con- 

 temporaneously have had a checkered history, full of ups and 

 downs, and the end is not yet, nor will the end be in sight 

 until the custom is abandoned of requiring at the same time so 

 many points as to put the matter beyond the range of practical 

 selection. 



The direct effect of too many points of selection is, first, 

 temptation to overlook, under the stress of circumstances, those 

 fundamental biological requirements, constitution and high 

 breeding powers ; and history shows that this has been repeat- 

 edly done, to the extinction of some of our otherwise most 

 promising creations. When this result does not follow, the 

 inevitable consequence of too many points of selection is that 

 we are forced to accept defects, now one and then another, as 

 has been shown, until, under Mendel's law, the breed becomes 



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