is usually
accompanied by a belligerent disposition on the part of the males. In
our ordinary barnyard fowl this trait is very evident. The rooster not
only domineers over the hens, not only struts about among them in
stately fashion and gives vent to his feelings by his sonorous voice,
he must also drive away from the neighborhood any rivals for the
affections of his wives. Hence the rooster attacks upon sight the
neighboring rooster, and battles with him to his entire discomfiture
and sometimes to the death.

Among the members of the deer family this particular phase of the
relation between the sexes has produced in the males, and only very
rarely in the females, the magnificent branching horns. These are
intended not so much as a protection against the enemy as for an
offensive weapon in the battle for the mates.

Beautiful and stately as are these magnificent horns, they last only
for a part of the year. We begin to understand their meaning. When the
wolf is hungriest, toward the close of the bitter winter, the deer is
without horns. When the time for mating comes, the deer within a few
weeks grows his horns, which at first are covered with a plushlike
coating, known as velvet. After a while this dries and he rubs his
horns against the trees until they are clean and smooth. Now he is
ready for the battle royal.

In the case of the fur seals polygamy has carried its specialization
of the males to a remarkable extent. The bull seals are several times
as large as the cows, and are provided with terrific canine teeth.
With these they battle with a violence that very often results in the
death of one of the combatants. A successful bull seal who has
gathered about him a cluster of seal cows is seamed and scarred with
the marks of his annual combats.

One more type of adaptation can be profitably considered. Animals have
developed many devices which serve for the protection of their young.
The wonderful silk spun by the spider was evidently primarily intended
to serve as a covering for the eggs. Probably all of our spiders agree
in using the silk for this purpose. Many of them employ it for
practically no other, though there are half a dozen different uses to
which different spiders may put their silk. Under these conditions we
have a right to infer that silk was primarily developed as a coating
for the eggs. In the case of some of our spiders a little fluffy mass
of silk covers the egg, while a firmly woven sheet o