Darwin's Artificial and Natural Selection 101 



that selection of fluctuating variations has been the only- 

 principle that has brought about these results. This is a 

 most important point, for, as we shall see, the central question 

 in the theory of natural selection has come to be whether 

 by the accumulation of fluctuating variations a new species 

 could ever be produced. If it be admitted that the evidence 

 from artificial selection is far from convincing, in showing 

 that selection of fluctuating variations could have been the 

 main source, even in the formation of new races, we need 

 not be prejudiced in favor of such a process, when we come 

 to examine the formation of species in nature. 



There are still other questions raised in this same chap- 

 ter, that demand serious consideration. Darwin writes as 

 follows : — 



" When we look to the hereditary varieties or races of our 

 domestic 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. Domestic 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 de- 

 gree 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 excep- 

 tions (and with that of the perfect fertility of varieties when 

 crossed, — a subject hereafter to be discussed), domestic 

 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 competent judges as mere varieties. If 

 any well-marked distinction existed between a domestic race 



