soil, the little beetles would in the same friendly way combine
their intelligences to overcome the artifice of Man. The same
combination of efforts has been noticed among the dung-beetles.

Even among animals standing at a somewhat lower stage of
organization we may find like examples. Some land-crabs of the
West Indies and North America combine in large swarms in order to
travel to the sea and to deposit therein their spawn; and each
such migration implies concert, co-operation, and mutual support.
As to the big Molucca crab (Limulus), I was struck (in 1882, at
the Brighton Aquarium) with the extent of mutual assistance which
these clumsy animals are capable of bestowing upon a comrade in
case of need. One of them had fallen upon its back in a corner of
the tank, and its heavy saucepan-like carapace prevented it from
returning to its natural position, the more so as there was in
the corner an iron bar which rendered the task still more
difficult. Its comrades came to the rescue, and for one hour's
time I watched how they endeavoured to help their
fellow-prisoner. They came two at once, pushed their friend from
beneath, and after strenuous efforts succeeded in lifting it
upright; but then the iron bar would prevent them from achieving
the work of rescue, and the crab would again heavily fall upon
its back. After many attempts, one of the helpers would go in the
depth of the tank and bring two other crabs, which would begin
with fresh forces the same pushing and lifting of their helpless
comrade. We stayed in the Aquarium for more than two hours, and,
when leaving, we again came to cast a glance upon the tank: the
work of rescue still continued! Since I saw that, I cannot refuse
credit to the observation quoted by Dr. Erasmus Darwin--namely,
that "the common crab during the moulting season stations as