OF CATTLE, ET AL. 301 



interbreeding of Horses. Could it have been, — what 

 there is so much throughout his books, to warrant 

 one in suspecting, — that Darwin guessed the true 

 secret of the in-and-in breeding process, and feared 

 lest, if he noted the Horse's exemption from the evil 

 results, the current conception of symmetry, which 

 attaches, peculiarly, to the Horse, would evoke the 

 truth, namely, that the proportionate development of 

 the characters of a species, is the sine qua non of per- 

 fect physiological condition ? 



The stipulation, with which we started, — viz., that 

 both the Refutation and the Converse Theory, would 

 be based exclusively upon Darwin's facts, — precludes 

 any detailed reference to the evidence, showing how 

 the Horse does withstand in-and-in breeding. It is a 

 matter of such common notoriety, however, that, pos- 

 sibly, any such evidence which Darwin might have 

 furnished, would be esteemed by the ' reader, as need- 

 less, furnished as the reader now has been with the 

 light afforded by the idea of Reversion. 



With respect to Cattle, and to Sheep, Darwin says 

 (p. 146, Vol. ii, Animals and Plants, &c): 



"With Cattle, there can be no doubt, that 

 extremely close-interbreeding may be long car- 

 RIED on; advantageously, with respect to external char- 

 acters, and with no manifestly apparent evil, as far as 

 constitution is concerned. The same remark is appli- 

 cable to Sheep. 



"Whether these animals have gradually been ren- 

 dered less susceptible, than others, to this evil, in order 

 to permit them to live in herds, — a habit which leads 

 the old and vigorous leaders to expel all intruders, 

 W 



