IV VARIATION UNDER DOMESTICATION 89 



our existing dogs have descended. But this intermixture of 

 distinct species will go a very little way in accounting for the 

 peculiarities of the different breeds of dogs, many of which are 

 totally unlike any wild animal. Such is the case with grey- 

 hounds, bloodhounds, bulldogs, Blenheim spaniels, terriers, 

 pugs, turnspits, pointers, and many others ; and these differ 

 so greatly in size, shape, colour, and habits, as well as in the 

 form and proportions of all the different parts of the body, 

 that it seems impossible that they could have descended from 

 any of the known Avild dogs, wolves, or allied animals, none 

 of which differ nearly so much in size, form, and proj^ortions. 

 We have here a remarkable proof that variation is not con- 

 fined to superficial characters — to the colour, hair, or external 

 appendages, when we see how the entire skeletons of such 

 forms as the greyhound and the bulldog have been gradually 

 changed in opposite directions till they are both completely 

 unlike that of any known wild animal, recent or extinct. 

 These changes have been the result of some thousands of years 

 of domestication and selection, different breeds being used and 

 preserved for different purposes ; but some of the best breeds 

 are kno^^^l to have been improved and perfected in modern 

 times. About the middle of the last century a new and im- 

 proved kind of foxhound was produced ; the gTeyhound was 

 also greatly improved at the end of the last century, while the 

 true bulldog was brought to perfection about the same period. 

 The Newfoundland dog has been so much changed since it was 

 first imported that it is now quite unlike any existing native 

 dog in that island. ^ 



Domestic Pigeons. 



The most remarkable and instructive example of variation 

 produced by human selection is afforded by the various races 

 and breeds of domestic pigeons, not only because the varia- 

 tions produced are often most extraordinary in amount and 

 diverse in character, but because in this case there is no 

 doubt whatever that all have been derived from one wild 

 species, the common rock-pigeon (Columba livia). As this is a 

 very important point it is well to state the evidence on which 

 the belief is founded. The ^Wld rock-j^igeon is of a slaty-blue 



^ See Darwin's Animals and Plants under Domestiadion, vol. i. pp. 40-42. 



