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P XI PHENOMENA OF ORGANIC NATURE 411 
ver might scarcely notice it, and yet every one of 
her children has an approximation to the same 
peculiarity to some extent. If you look at the 
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other extreme, too, the gravest diseases, such as 
gout, scrofula, and consumption, may be handed 
_ down with just the same certainty and persistence 
as we noticed in the perpetuation of the bandy 
legs of the Ancon sheep. 
However, these facts are best illustrated in 
animals, and the extent of the variation, as is well 
known, is very remarkable in dogs. For example, 
_ there are some dogs very much smaller than others; 
indeed, the variation is so enormous that probably 
the smallest dog would be about the size of the 
head of the largest ; there are very great variations 
in the structural forms not only of the skeleton 
_ but also in the shape of the skull, and in the pro- 
_ portions of the face and the disposition of the teeth. 
The Pointer, the Retriever, Bulldog, and the 
_ Terrier differ very greatly, and yet there is every 
reason to believe that every one of these races 
has arisen from the same source,—that all the 
- most important races have arisen by this selective 
_ breeding from accidental variation. 
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A still more striking case of what may be done 
by selective breeding, and it is a better case, be- 
cause there is no enes of that partial infusion of 
error to which I alluded, has been studied very 
_ carefully by Mr. Darwin,—the case of the domestic 
pigeons. I dare say there may be some among you 
