. So she rubs the remnant of it off against
stones or the bark of trees, and re-develops a similar back afresh at
the next breeding season.

Almost never do we find a device in nature which occurs once only. The
unique hardly exists: nature is a great copyist. At least two animals
of wholly unlike kinds are all but sure to hit independently upon the
self-same mechanism. So it is not surprising to learn that a cat-fish
has invented an exactly similar mode of carrying its young to that
adopted by the Surinam toad: only, here it is on the under surface,
not the upper one, that the spawn is plastered. The eggs of this
cat-fish, whose scientific name is Aspredo, are pressed into the skin
below the body, and so borne about by the mother till they hatch. This
is the second instance of which I spoke above, where the female fish
herself assumes the care of her offspring, instead of leaving it
entirely to her excellent partner.

Higher up in the scale of life we get many instances which show
various stages in the same progressive development towards greater
care for the safety and education of the young. Among the larger
lizards, for example, a distinct advance may be traced between the
comparatively uncivilized American alligator and his near ally, the
much more cultivated African crocodile. On the banks of the
Mississippi, the alligator lays a hundred eggs or thereabouts, which
she deposits in a nest near the water's edge, and then covers them up
with leaves and other decaying vegetable matter. The fermentation of
these leaves produces heat and so does for the alligator's eggs what
sitting does for those of hens and other birds: the mother deputes her
maternal functions, so to speak, to a festering heap of decomposing
plant-refuse. Nevertheless, she loiters about all the time, like
Miriam round the ark which contained Moses, to see what happens; and
when the eggs hatch out, she leads her little ones down to the river,
and there makes alligators of them. This is a simple and relatively
low stage in the nursery arrangements of the big lizards.

The African crocodile, on the other hand, goes a stage higher. It lays
only about thirty eggs, but these it buries in warm sand, and then
lies on top of them at night, both to protect them from attack and to
keep them warm during the cooler hours. In short, it sits upon them.
When the young crocodiles within the eggs are ready to hatch, they
utter an acute cry. The mother then digs down