tself, but wrongs others. It disobeys the
fundamental law of its own being, and taxes the innocent to contribute
to its disgrace. So that if Nature is just, if Nature has an avenging
hand, if she holds one vial of wrath more full and bitter than another,
it shall surely be poured out upon those who are guilty of this double
sin. Let us see what form this punishment takes.

Observant visitors to the sea-side, or let us say to an aquarium, are
familiar with those curious little creatures known as Hermit-crabs. The
peculiarity of the Hermits is that they take up their abode in the
cast-off shell of some other animal, not unusually the whelk; and here,
like Diogenes in his tub, the creature lives a solitary, but by no means
an inactive life.

The _Pagurus_, however, is not a parasite. And yet although in no sense
of the word a parasite, this way of inhabiting throughout life a house
built by another animal approaches so closely the parasitic habit, that
we shall find it instructive as a preliminary illustration, to consider
the effect of this free-house policy on the occupant. There is no
doubt, to begin with, that, as has been already indicated, the habit is
an acquired one. In its general anatomy the Hermit is essentially a
crab. Now the crab is an animal which, from the nature of its
environment, has to lead a somewhat rough and perilous life. Its days
are spent among jagged rocks and boulders. Dashed about by every wave,
attacked on every side by monsters of the deep, the crustacean has to
protect itself by developing a strong and serviceable coat of mail.

How best to protect themselves has been the problem to which the whole
crab family have addressed themselves; and, in considering the matter,
the ancestors of the Hermit-crab hit on the happy device of re-utilizing
the habitations of the molluscs which lay around them in plenty,
well-built, and ready for immediate occupation. For generations and
generations accordingly, the Hermit-crab has ceased to exercise itself
upon questions of safety, and dwells in its little shell as proudly and
securely as if its second-hand house were a fortress erected especially
for its private use.

Wherein, then, has the Hermit suffered for this cheap, but real solution
of a practical difficulty? Whether its laziness costs it any moral
qualms, or whether its cleverness becomes to it a source of
congratulation, we do not know; but judged from the appearance the
animal makes under the