g a
narrow opening in front, through which the small hippocampi creep out
one by one as soon as they consider themselves capable of buffeting the
waves of the Adriatic.

Fish that take much care of their offspring naturally don't need to
produce eggs in the same reckless abundance as those dissipated kinds
that leave their spawn exposed on the bare sandy bottom, at the mercy
of every comer who chooses to take a bite at it. They can afford to lay
a smaller number, and to make each individual egg much larger and
richer in proportion than their rivals. This plan, of course, enables
the young to begin life far better provided with muscles and fins than
the tiny little fry which come out of the eggs of the improvident
species. For example, the cod-fish lays nine million odd eggs; but
anybody who has ever eaten fried cod's-roe must needs have noticed that
each individual ovum was so very small as to be almost indistinguishable
to the naked eye. Thousands of these infinitesimal specks are devoured
before they hatch out by predaceous fish; thousands more of the young
fry are swallowed alive during their helpless infancy by the enemies of
their species. Imagine the very fractional amount of parental affection
which each of the nine million must needs put up with! On the other
hand, there is a paternally-minded group of cat-fish known as the genus
_Arius_, of Ceylon, Australia, and other tropical parts, the males of
which carry about the ova loose in their mouths, or rather in an
enlargement of the pharynx, somewhat resembling the pelican's pouch;
and the spouses of these very devoted sires lay accordingly only very
few ova, all told, but each almost as big as a hedge-sparrow's egg--a
wonderful contrast to the tiny mites of the cod-fish. To put it
briefly, the greater the amount of protection afforded the eggs, the
smaller the number and the larger the size. And conversely, the larger
the size of the egg to start with, the better fitted to begin the
battle of life is the young fish when first turned out on a cold world
upon his own resources.

This is a general law, indeed, that runs through all nature, from
London slums to the deep sea. Wasteful species produce many young, and
take but little care of them when once produced. Economical species
produce very few young, but start each individual well-equipped for its
place in life and look after them closely till they can take care of
themselves in the struggle for existence. And