HYBRIDISM. 145 
their mingling and selection, and naturally they were 
originally derived from a single primary ancestor, com- 
mon to the whole genus. In no case is each separate 
cultivated race descended from a distinct wild species. 
In opposition to this, almost all farmers and gardeners 
maintain, with the greatest confidence, that each separate race 
bred by them must be descended from a separate wild 
_ primary species, because they clearly perceive the differences 
of the races, and attach very high importance to the inherit- 
ance of their qualities ; but they do not take into consider- 
ation the fact that these qualities have arisen only by the 
slow accumulation of small and scarcely observable changes. 
In this respect it is extremely instructive to compare culti- 
vated races with wild species. 
Many naturalists, and especially the opponents of the 
Theory of Development, have taken the greatest trouble to 
discover some morphological or physiological mark, some 
characteristic property, whereby the artificially bred and 
cultivated races may be clearly and thoroughly distin- 
guished from wild species which have arisen naturally. 
All these attempts have completely failed, and have led 
only with increasing certainty to the result, that such a 
distinction is altogether impossible. I have minutely dis- 
cussed this fact, and illustrated it by examples in my criti- 
cism of the idea of species. (Gen. Morph. ii. 323-364.) 
I may here briefly touch on yet another side of this 
question, because not only the opponents, but even a few of 
the most distinguished followers of Darwin—for example, 
Huxley—have regarded the phenomena of bastard-breeding, 
or hybridism, as one of the weakest points of Darwinism. 
Between cultivated races and wild species, they say, there 
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