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 
