a 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 occasionally to
find gradations of important structures between the different castes
of neuters in the same species, that I gladly availed myself of Mr. F.
Smith's offer of numerous specimens from the same nest of the driver
ant (Anomma) of West Africa. The reader will perhaps best appreciate
the amount of difference in these workers by my giving, not the actual
measurements, but a strictly accurate illustration: the difference was
the same as if we were to see a set of workmen building a house, of whom
many were five feet four inches high, and many sixteen feet high; but we
must in addition suppose that the larger workmen had heads four instead
of three times as big as those of the smaller men, and jaws nearly five
times as big. The jaws, moreover, of the working ants of the several
sizes differed wonderfully in shape, and in the form and number of the
teeth. But the important fact for us is that, though the workers can
be grouped into castes of different sizes, yet they graduate insensibly
into each other, as does the widely-different structure of their jaws. I
speak confidently on this latter point, as Sir J. Lubbock made drawings
for me, with the camera lucida, of the jaws which I dissected from the
workers of the several sizes. Mr. Bates, in his interesting "Naturalist
on the Amazons," has described analogous cases.

With these facts before me, I believe that natural selection, by acting
on the fertile ants or parents, could form a species which should
regularly produce neuters, all of large size with one form of jaw, or
all of small size with widely different jaws; or lastly, and this is the
greatest difficulty, one set of workers of one size and structure, and
simultaneously another set of workers of a different size and structure;
a graduated series having first been formed, as in the case of the
driver ant, and then the extreme forms having been produced in greater
and greater numbers, through the survival of the parents which generated
them, until none with an intermediate structure were produced.

An analogous explanation has been given by Mr. Wallace, of the equally
complex case, of certain Malayan butterflies regularly appearing under
two or even three distinct female forms; and by Fritz Muller, of certain
Brazilian crustaceans likewise appea