ce to
inhabiting freshwater rivers; or, _vice-versa,_ when a freshwater kind,
moved by an aspiration for more expansive surroundings, takes up its
residence in the sea as a naturalised marine. Whenever such a change of
address happens, it usually follows that the young fry cannot stand the
conditions of the new home to which their ancestors were
unaccustomed--we all know the ingrained conservatism of children--and
so the parents are obliged once a year to undertake a pilgrimage to
their original dwelling-place for the breeding season.

Extreme cases of terrestrial animals, once aquatic in habits, throw a
flood of lurid light (as the newspapers say) upon the reason why this
should be so. For example, frogs and toads develop from tadpoles, which
in all essentials are true gill-breathing fish. It is, therefore,
obvious that they cannot lay their eggs on dry land, where the tadpoles
would be unable to find anything to breathe; so that even the driest
and most tree-haunting toads must needs repair to the water once a year
to deposit their spawn in its native surroundings. Once more, crabs
pass their earlier larval stages as free-swimming crustaceans, somewhat
shrimp-like in appearance, and as agile as fleas: it is only by gradual
metamorphosis that they acquire their legs and claws and heavy
pedestrian habits. Now there are certain kinds of crab, like the West
Indian land-crabs (those dainty morsels whose image every epicure who
has visited the Antilles still enshrines with regret in a warm corner
of his heart), which have taken in adult life to walking bodily on
shore, and visiting the summits of the highest mountains, like the fish
of Deucalion's deluge in Horace. But once a year, as the land-crabs
bask in the sun on St. Catherine's Peak or the Fern Walk, a strange
instinctive longing comes over them automatically to return for a while
to their native element; and, obedient to that inner monitor of their
race, down they march in thousands, _velut agmine facto_, to lay their
eggs at their leisure in Port Royal harbour. On the way, the negroes
catch them, all full of rich coral, waiting to be spawned; and Chloe or
Dinah, serves them up hot, with breadcrumbs, in their own red shells,
neatly nestling between the folds of a nice white napkin. The rest run
away, and deposit their eggs in the sea, where the young hatch out, and
pass their larval stage once more as free and active little swimming
crustaceans.

Well, crabs, I nee