90 



THE PEKPETUATION OF LIVING BEINGS, 



the Otter breed of sheep, the wool of which was infe- 

 rior to that of the Merino, was gradually allowed to die 

 out. 



You see that these facts illustrate perfectly well 

 what may be done if you take care to breed from stocks 

 that are similar to each other. After having got a 

 variation, if, by crossing a variation with the original 

 stock, you multiply that variation, and then take care 

 to keep that variation distinct from the original stock, 

 and make them breed together, — then you may almost 

 certainly produce a race whose tendency to continue 

 the variation is exceedingly strong. 



This is what is called " selection ; " and it is by exactly 

 the same process as that by which Seth Wright bred his 

 Ancon sheep, that our breeds of cattle, dogs, and fowls, 

 are obtained. There are some possibilities of excep- 

 tion, but still, speaking broadly, I may say that this is 

 the way in which all our varied races of domestic ani- 

 mals have arisen ; and you must understand that it is 

 not one peculiarity or one characteristic alone in which 

 animals may vary. There is not a single peculiarity 

 or characteristic of any kind, bodily or mental, in which 

 offspring may not vary to a certain extent from the 

 parent and other animals. 



Among ourselves this is well known. The simplest 

 physical peculiarity is mostly reproduced. I know a 

 case of a man whose wife has the lobe of one her ears 

 a little flattened. An ordinary observer might scarcely 

 notice it, and yet every one of her children has an 

 approximation to the same peculiarity to some ex- 

 tent. 



If you look at the other extreme, too, the gravest 

 diseases, such as gout, scrofula, and consumption, may 



