HEREDITARY TRANSMISSION AND VARIATION. 97 



be handed down with just the same certainty and per- 

 sistence 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 dis- 

 position of the teeth. 



The Pointer, the Eetriever, Bulldog, and the Ter- 

 rier, 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 allude, has been studied very carefully by Mr. Dar- 

 win, — 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 ap- 

 proaching the subject, I would speak with all humility 

 and hesitation, as I regret to say that I am not a pigeon 

 fancier. I know it is a great art and mystery, and a 

 thing upon which a man must not speak lightly ; but 

 I shall endeavour, as far as my understanding goes, to 

 give you a summary of the published and unpublished 

 information which I have gained from Mr. Darwin. 

 5 



