CEEATION BY LAW. 293 



terrestrial conditions, has been long ago reached. 

 In cases, however, where this limit had not been so 

 nearly reached as in the horse, we have been enabled 

 to make a more marked advance and to produce a 

 greater difference of form. The wild dog is an animal 

 that hunts much in company, and trusts more to en- 

 durance than to speed. Man has produced the grey- 

 hound, which differs much more from the wolf or the 

 dingo than the racer does from the wild Arabian. 

 Domestic dogs, again, have varied more in size and 

 in form than the whole family of Canidae in a state 

 of nature. No wild dog, fox, or wolf, is either so 

 small as some of the smallest terriers and spaniels, 

 or so large as the largest varieties of hound or New- 

 foundland dog. And, certainly, no two wild animals 

 of the family differ so widely in form and proportions 

 as the Chinese pug and the Italian greyhound, or the 

 bulldog and the common greyhound. The known range 

 of variation is, therefore, more than enough for the 

 derivation of all the forms of Dogs, Wolves, and Foxes 

 from a common ancestor. 



Again, it is objected that the Pouter or the Fan- 

 tail pigeon cannot be further developed in the same 

 direction. Variation seems to have reached its limits 

 in these birds. But so it has in nature. The Fan- 

 tail has not only more tail feathers than any of the 

 three hundred and forty existing species of pigeons, 

 but more than any of the eight thousand known 

 species of birds. There is, of course, some limit to 

 the number of feathers of which a tail useful for flight 



