It will indeed be thought that I have an overweening confidence in the
principle of natural selection, when I do not admit that such
wonderful and well-established facts at once annihilate my theory. In
the simpler case of neuter insects all of one caste or of the same
kind, which have been rendered by natural selection, as I believe to
be quite possible, different from the fertile males and females,--in
this case, we may safely conclude from the analogy of ordinary
variations, that each successive, slight, profitable modification did
not probably at first appear in all the individual neuters in the same
nest, but in a few alone; and that by the long-continued selection of
the fertile parents which produced most neuters with the profitable
modification, all the neuters ultimately came to have the desired
character. On this view we ought occasionally to find neuter-insects
of the same species, in the same nest, presenting gradations of
structure; and this we do find, even often, considering how few
neuter-insects out of Europe have been carefully examined. Mr. F.
Smith has shown how surprisingly the neuters of several British ants
differ from each other in size and sometimes in colour; and that the
extreme forms can sometimes be perfectly linked together by
individuals taken out of the same nest: I have myself compared perfect
gradations of this kind. It often happens that the larger or the
smaller sized workers are the most numerous; or that both large and
small are numerous, with those of an intermediate size scanty in
numbers.
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