12 THE ORIGIN OF SPECIES 



CHARACTER OF DOMESTIC VARIETIES; DIFFICULTY OF DISTINGUISH- 

 ING BETWEEN VARIETIES AND SPECIES; ORIGIN OF DOMESTIC 

 VARIETIES FROM ONE OR MORE SPECIES 



When we look to the hereditary varieties or races of our do- 

 mestic animals and plants, and compare them with closely allied 

 species, we generally perceive in each domestic race, as already 

 remarked, less uniformity of character than in true species. Do- 

 mestic races often have a somewhat monstrous character; by 

 which I mean, that, although differing from each other and from 

 other species of the same genus, in several trifling respects, they 

 often differ in an extreme degree in some one part, both when 

 compared one with another, and more especially when compared 

 with the species under nature to which they are nearest allied. 

 With these exceptions (and with that of the perfect fertility of 

 varieties when crossed — a subject hereafter to be discussed), do- 

 mestic races of the same species differ from each other in the same 

 manner as do the closely allied species of the same genus in a state 

 of nature, but the differences in most cases are less in degree. This 

 must be admitted as true, for the domestic races of many animals 

 and plants have been ranked by some competent judges as the 

 descendants of aboriginally distinct species, and by other com- 

 petent judges as mere varieties. If any well-marked distinction 

 existed between a domestic race and a species, this source of doubt 

 would not so perpetually recur. It has often been stated that do- 

 mestic races do not differ from each other in characters of generic 

 value. It can be shown that this statement is not correct; but 

 naturalists differ much in determining what characters are of 

 generic value; all such valuations being at present empirical. When 

 it is explained how genera originate under nature, it will be seen 

 that we have no right to expect often to find a generic amount of 

 difference in our domesticated races. 



In attempting to estimate the amount of structural difference 

 between allied domestic races, we are soon involved in doubt, from 

 not knowing whether they are descended from one or several 

 parent species. This point, if it could be cleared up, would be in- 

 teresting; if, for instance, it could be shown that the greyhound, 

 bloodhound, terrier, spaniel, and bull-dog, which we all know 

 propagate their kind truly, were the offspring of any single spe- 

 cies, then such facts would have great weight in making us doubt 

 about the immutability of the many closely allied natural species 

 — for instance, of the many foxes — inhabiting the different quar- 

 ters of the world. I do not believe, as we shall presently see, that 



