from not being blown out to sea; and, on the other
hand, those beetles which most readily took to flight would oftenest have
been blown to sea and thus have been destroyed.

The insects in Madeira which are not ground-feeders, and which, as the
flower-feeding coleoptera and lepidoptera, must habitually use their wings
to gain their subsistence, have, as Mr. Wollaston suspects, their wings not
at all reduced, but even enlarged. This is quite compatible with the action
of natural selection. For when a new insect first arrived on the island,
the tendency of natural selection to enlarge or to reduce the wings, would
depend on whether a greater number of individuals were saved by
successfully battling with the winds, or by giving up the attempt and
rarely or never flying. As with mariners shipwrecked near a coast, it would
have been better for the good swimmers if they had been able to swim still
further, whereas it would have been better for the bad swimmers if they had
not been able to swim at all and had stuck to the wreck. {137}

The eyes of moles and of some burrowing rodents are rudimentary in size,
and in some cases are quite covered up by skin and fur. This state of the
eyes is probably due to gradual reduction from disuse, but aided perhaps by
natural selection. In South America, a burrowing rodent, the tuco-tuco, or
Ctenomys, is even more subterranean in its habits than the mole; and I was
assured by a Spaniard, who had often caught them, that they were frequently
blind; one which I kept alive was certainly in this condition, the cause,
as appeared on dissection, having been inflammation of the nictitating
membrane. As frequent inflammation of the eyes must be injurious to any
animal, and as eyes are certainly not indispensable to animals with
subterranean habits, a reduction in their size with the adhesion of the
eyelids and growth of fur over them, might in such case be an advantage;
and if so, natural selection would constantly aid the effects of disuse.

It is well known that several animals, belonging to the most different
classes, which inhabit the caves of Styria and of Kentucky, are blind. In
some of the crabs the foot-stalk for the eye remains, though the eye is
gone; the stand for the telescope is there, though the telescope with its
glasses has been lost. As it is difficult to imagine that eyes, though
useless, could be in any way injurious to animals living in darkness, I
attribute their loss wholly to