202 PRINCIPLES OF STOCK-BREEDING. 



Merino rams, than by uniting the Aveyron breed with 

 the same rams, but he was disappointed. 



".The Roussillon race, being 110 doubt more ancient 

 and possessed of greater potency (force motrice) than 

 the Aveyron race, offered greater resistance than the 

 latter to the influence of the Merinos; and, after 

 twenty-five years of successive crossing, the primitive 

 characters of the Eoussillons still appeared, while the 

 crosses of the Aveyron race, after the same length of 

 time, could not be distinguished from the Spanish 

 sheep. It thus appears that characters long estab- 

 lished, and thoroughly incorporated with the consti- 

 tution by transmission through many successive gen- 

 erations, give to a race or breed a certain fixity of 

 type something of the persistency and individuality 

 of a species, by which it is enabled to resist, for a 

 length of time, fusion with another race, and continue 

 to reproduce its leading characteristics." * 



It has been said that " the persons who chiefly re- 

 sort to crossing are those who have, up to the present 

 time, kept but a very inferior description of stock," a 

 and this is, without doubt, the reason why cross- 

 breeding has been found to be, in such cases, an im- 

 portant means of improvement. 



In all cases in which cross-breeding has been suc- 

 cessfully practised, the object in view has been pre- 

 cisely the same, and the reasons that have led to it are 

 identical with those that have induced the improvers 

 of the pure breeds to resort to the opposite system of 

 in-and-in breeding. 



1 Journal of the Highland Agricultural Society, 185Y-'59, p. 29. 

 a Journal of the Royal Agricultural Society, vol. xxiii., p. 352. 



