ngs, and the receptaculum seminis, and their
compound eyes have degenerated to a few facets. How could this last
change have come about through disuse, since the eyes of workers are
exposed to light in the same way as are those of the sexual insects and
thus in this particular case are not liable to "disuse" at all? The same
is true of the receptaculum seminis, which can only have been disused
as far as its glandular portion and its stalk are concerned, and also
of the wings, the nerves tracheae and epidermal cells of which could
not cease to function until the whole wing had degenerated, for the
chitinous skeleton of the wing does not function at all in the active
sense.

But, on the other hand, the workers in all species have undergone
modifications in a positive direction, as, for instance, the greater
development of brain. In many species large workers have evolved,--the
so-called SOLDIERS, with enormous jaws and teeth, which defend the
colony,--and in others there are SMALL workers which have taken over
other special functions, such as the rearing of the young Aphides. This
kind of division of the workers into two castes occurs among several
tropical species of ants, but it is also present in the Italian species,
Colobopsis truncata. Beautifully as the size of the jaws could be
explained as due to the increased use made of them by the "soldiers," or
the enlarged brain as due to the mental activities of the workers, the
fact of the infertility of these forms is an insurmountable obstacle
to accepting such an explanation. Neither jaws nor brain can have been
evolved on the Lamarckian principle.

The problem of coadaptation is no easier in the case of the ant than in
the case of the Giant Stag. Darwin himself gave a pretty illustration to
show how imposing the difference between the two kinds of workers in one
species would seem if we translated it into human terms. In regard to
the Driver ants (Anomma) we must picture to ourselves a piece of work,
"for instance the building of a house, being carried on by two kinds of
workers, of which one group was five feet four inches high, the other
sixteen feet high." ("Origin of Species" (6th edition), page 232.)

Although the ant is a small animal as compared with man or with the
Irish Elk, the "soldier" with its relatively enormous jaws is hardly
less heavily burdened than the Elk with its antlers, and in the ant's
case, too, a strengthening of the skeleton, of the muscles,