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 wild dogs, wolves, or allied animals, none 
of which differ nearly so much in size, form, and proportions. 
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 known 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 greyhound 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. 1 
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 wild rock-pigeon is of a slaty-blue 
1 See Darwin’s Animals and Plants under Domestication, vol. i. pp. 40-42. 
