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. Formica flava has larger and smaller workers, with some of
intermediate size; and, in this species, as Mr. F. Smith has observed,
the larger workers have simple eyes (ocelli), which though small can
be plainly distinguished, whereas the smaller workers have their ocelli
rudimentary. Having carefully dissected several specimens of these
workers, I can affirm that the eyes are far more rudimentary in the
smaller workers than can be accounted for merely by their proportionally
lesser size; and I fully believe, though I dare not assert so
positively, that the workers of intermediate size have their ocelli in
an exactly intermediate condition. So that we here have two bodies of
sterile workers in the same nest, differing not only in size, but
in their organs of vision, yet connected by some few members in an
intermediate condition. I may digress by adding, that if the smaller
workers had been the most useful to the community, and those males and
females had been continually selected, which produced more and more
of the smaller workers, until all the workers had come to be in this
condition; we should then have had a species of ant with neuters very
nearly in the same condition with those of Myrmica. For the workers of
Myrmica have not even rudiments of ocelli, though the male and female
ants of this genus have well-developed ocelli.

I may give one other case: so confidently did I expect to find
gradat