SELECTION'S IN BREEDING. 35 



bred mares can not be embraced in the list of trotters, unless in rare 

 instances. The tendency was to work back toward the original blood, 

 and that was the blood of a race-horse and not a trotter. 



In this connection the following extracts are both suggestive and 

 full of sound pliilosophy: 



It is one of the principles of heredity, that wlien there is great uniformity 

 in a species, divergences from the usual type in the offspring are slight and 

 rare ; but when this uniformity, from no matter what cause, has been broken 

 up, divergences in the offspring are frequent and great, although there is- 

 always present a tendency, more or less powerful, to revert to the original 

 type. This tendency is most frequently manifested when breeds or races, 

 widely differing in their present forms, are crossed upon each other. In such 

 cases, or violent crosses, as they are called, it frequently happens that the 

 progeny resembles neither parent, but shows strong marks of the type from 

 which both of its ancestors originally sprung. Darwin, in his work, already 

 referred to, gives numerous illustrations of this tendency to reversion, in his 

 experiments with pigeons of various breeds and colors, one of which we quote, 

 as follows : 



"I paired a mongrel female barbfautail with a mongrel male barb-spot; 

 neither of which mongrels had the least blue about them. Let it be remem- 

 bered that blue barbs are excessively rare; that spots, as has been already 

 stated, were perfectly characterized in the year 1676, and breed perfectly true ; 

 this likewise is the case with white fantails, so much so that I have never 

 heard of white fantails throwing any other color. Nevertheless the offspring 

 from the above two mongrels were of exactly the same blue tint as that of the 

 wild rock-pigeon, from the Shetland Islands, over the whole back and wings ; 

 the double black wing-bars were equally conspicuous ; the tail was exactly 

 alike in all its characters, and the croup was pure white; the head, however, 

 was tinted with a shade of red, evidently derived from the spot, and was of a 

 paler blue than in the rock-pigeon, as was the stomach. So that two black 

 barbs, a red spot, and a white fantail, as the four purely-bred grandparents, 

 produced a bird of the same general blue color, together with every character- 

 istic mark, as in the wild Columba liviay 



This tendency to reversion in different breeds of domestic animals when 

 crossed, accounts for many of the disappointments which breeders experience 

 in their efforts to improve their stock, and serves greatly to complicate the 

 breeding problem. 



This matter may be of some importance to those amateur breeders 

 who are constantly demanding that Ave should have more frequent 

 recurrence to the blood of the thoroughbred to give stamina and 

 hio:h quality to our roadsters, and is thrown in here as germane to the 

 subject particularly under consideration, although the topic last referred 

 to is specially treated in a subsequent chapter. 



Another important truth is very frequently overlooked — not being 



