r, "mad with
excitement," as Darwin well phrased it, looking his handsomest and
best with his lustrous colours glistening like an opal. If she will
listen to his suit, he grows wild with delight, and coaxes her into
the nest with most affectionate endearments. In No. 2, as you
perceive, the mate of his choice has been induced to enter, and is
laying her eggs in the dainty home his care has provided for her. The
father fish, meanwhile dances and capers around, in a _pas de
triomphe_ at the success of his endeavors.

One wife, however, does not suffice to fill the nest with eggs; and
the stickleback is a firm believer in the advantages of large
families. So, as soon as his first mate has laid all her spawn, he
sets out once more in search of another. Thus he goes on until the
home is quite full of eggs, bringing back one wife after another, in
proportion to his success in wooing and fighting. For, like almost all
polygamists, your stickleback is a terrible fighter. The males join
wager of battle with one another for possession of their mates; in
their fierce duels they make fearful use of the formidable spines on
their backs, sometimes entirely ripping up and cutting to pieces their
ill-fated adversary. The spines thus answer to the spurs of the
gamecock or the antlers of the deer; they are masculine weapons in the
struggle for mates. Indeed, you may take it for granted that brilliant
colors and decorative adjuncts in animals almost invariably go with
irascible tempers, pugnacious habits, and the practice of fighting for
the possession of the harem. The consequence is, with the
sticklebacks, that many males get killed during the struggle for
supremacy, so that the survivors wed half a dozen wives each, like
little Turks that they are in their watery seraglios. Only the most
beautiful and courageous fish succeed in gaining a harem of their own:
and thus the wager of battle tells in the end for the advantage of the
race, by eliminating the maimed, the ugly, and the cowardly, and
encouraging the strong, the handsome, the enterprising, and the
valiant. This is nature's way of preventing degeneracy.

In No. 3 the nest is seen full of eggs, and the excellent father now
comes out in his best light as their guardian and protector. He
watches over them with ceaseless care, freeing them from parasites,
and warding off the attacks of would-be enemies who desire to devour
them, even though the intruder be several times his own size