327 



all the characters of their species, and, therefore, the 

 less are the differences between them. It is, only when 

 each variety lacks very much that the other crossed 

 variety possesses, that great good results. There is 

 but little margin, for increase of good, with varieties of 

 Cattle and of Sheep, because those varieties, generally, 

 have nearly all the development, which is required for 

 perfection. The results from crossing varieties of 

 these last-named species, are generally shown, mainly, 

 in increase of size, and in some accession of vigor. 



Darwin says (p. 149, Vol. ii, Animals and Plants, &c.) : 



"Although, by the aid of careful selection, the near 

 interbreeding of sheep, may be long continued, without 

 any manifest evil, yet it has often been the practice, 

 with farmers, to cross distinct breeds, to obtain animals 

 for the butcher, which plainly shows that good is de- 

 rived from this practice. Mr. Spooner sums up his 

 excellent Essay on Crossing, by asserting, that there 

 is a direct pecuniary advantage, in judicious cross- 

 breeding, especially, when the male is larger than the 

 female. A former celebrated breeder,- Lord Somer- 

 ville, distinctly states, that his half-breeds from Rye- 

 lands and Spanish sheep, were larger animals than, 

 either, the pure Ryelands, or pure Spanish sheep." 



The reason of the increase of size, attendant upon 

 crossing, is not only because of reversion to the original 

 type (which was of a size, sufficient to cover any at 

 present existing individual of the given species), but, 

 also because greater size, or room, is demanded in the 

 offspring of a cross, in order to accommodate the pecu- 

 liarities of both parents. The reason, increase of size 

 from a cross, is especially observable, when the male is 



