HEREDITARY TRANSMISSION AND VARIATION. 101 



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 other extreme; too, the 

 gravest diseases, such as gout, scrofula, and consump- 

 tion, 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 proportions 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. 



A still more striking case of what may be done by 

 selective breeding, and it is a better case, because 

 there is no chance 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 who may be 

 pigeon fanciers, and I wish you to understand that 

 in approaching the subject, I would speak with all 



