HEREDITARY TRANSMISSION AND VARIATION. 99 



were introduced ; and as their wool was much more 

 valuable, and as they were a quiet race of sheep, 

 and showed no tendency to trespass or jump over 

 fences, the Otter breed of sheep, the wool of which 

 was inferior to that of the Merino, was gradually 

 allowed to die out. 



You see that these facts illustrate perfectly well 

 what maybe done if you take care to breed from stocks 

 that are similar to each other. After having got a varia- 

 tion, 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 cer- 

 tainly 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 

 exception, but still, speaking broadly, I may say that 

 this is the way in which all our varied races of domestic 

 animals 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 woman who has the lobe of one of her 

 ears a little flattened. An ordinary observer might 



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