The Descent of Man

ce. See also Mr. Bates, in 'Proc. Entomolog. Soc.'
Nov. 19, 1866, p. xl.) that the females of some
species are extremely variable, the males being
nearly constant. In a future chapter I shall have
occasion to shew that the beautiful eye-like
spots, or ocelli, found on the wings of many
Lepidoptera, are eminently variable. I may here
add that these ocelli offer a difficulty on the
theory of sexual selection; for though appearing
to us so ornamental, they are never present in
one sex and absent in the other, nor do they
ever differ much in the two sexes. (25. Mr. Bates
was so kind as to lay this subject before the
Entomological Society, and I have received
answers to this effect from several entomologists.)
This fact is at present inexplicable; but if
it should hereafter be found that the formation
of an ocellus is due to some change in the tissues
of the wings, for instance, occurring at a
very early period of development, we might
expect, from what we know of the laws of inheritance,
that it would be transmitted to both