young are hatched. This case is exactly analogous to that of the doves
among birds: I may add that wherever such instances occur they always
seem to be accompanied by a markedly gentle and affectionate nature.
Brilliantly-coloured fighting polygamous fishes are fierce and cruel:
monogamous and faithful animals are seldom bright-hued, but they mate
for life and are usually remarkable for their domestic felicity. The
doves and love-birds are familiar instances.

Frogs are very closely allied to fish: indeed, one may almost say that
every frog begins life as a fish, limbless, gill-bearing, and aquatic,
and ends it as something very like a reptile, four-legged,
lung-bearing, and more or less terrestrial. For the tadpole is
practically in all essentials a fish. It is not odd, therefore, to
find that certain frogs reproduce, in a very marked manner, the
fatherly traits of their fish-like ancestors. There is a common kind
of frog in France, Belgium, and Switzerland, which does not extend to
England, but which closely recalls the habits of the stickleback and
the pipe-fish. Among these eminently moral amphibians, it is the
father, not the mother, who takes entire charge of the family. The
female lays her spawn in the shape of long strings or rolls, looking
at first sight like slimy necklaces. I have seen them as much as a
couple of yards long, lying loose on the grass where the frog lays
them. As soon as she has deposited them, however, the father frog hops
up, twists the garlands dexterously in loose festoons round his legs
and thighs, and then retires with his precious burden to some hole in
the bank of his native pond, where he lurks in seclusion till the eggs
develop. Frogs do not need frequent doses of food--their meals are
often few and far between--and during the six or eight weeks that the
eggs take to mature the father probably eats very little, though he
may possibly sally forth at night, unobserved, in search of provender.