supposed, by the advocates of the origin of species by natural
selection, to have been brought about by varieties of one species
somewhat resembling another having special means of protection, and
preserved from their enemies in consequence of that unconscious
imitation. The resemblance, which was perhaps at first only remote,
is supposed to have been increased in the course of ages by the
varieties being protected that more and more closely approached the
species imitated, in form, colour, and movements. These
resemblances are not only between insects of different genera and
orders, but between insects and flowers, leaves, twigs, and bark of
trees, and between insects and inanimate nature. They serve often
for concealment, as when leaves are imitated by leaf-insects and
many butterflies, or for a disguise that enables predatory species
to get within reach of their prey, as in those spiders that
resemble the petals of flowers amongst which they hide.

(PLATE 1. ALLIGATORS IN SAN JUAN RIVER.)

That I may not travel over the same ground twice, I may here
mention that on a subsequent visit to Greytown I rode a few miles
northward along the beach. On my return, I tied up the horse and
walked about a mile over the sand-bank that extends down to the
mouth of the river. A long, deep branch forms a favourite resort
for alligators. At the far end of a sand-spit, near where some low
trees grew, I saw several dark objects lying close to the water on
the shelving banks. They were alligators basking in the sun. As I
approached, most of them crawled into the water. Mr. Hollenbeck had
been down a few days before shooting at them with a rifle, to try
to get a skull of one of the monsters, and I passed a dead one that
he had shot. As I walked up the beach, I saw many that were not