permits no other male to intrude
upon its acre or so of ground during the early hours of the morning, but
for the rest of the day it joins the flock and is sociable; the
Herring-Gull resents the approach of strangers so long as it occupies
its few square feet of cliff, but welcomes companions whilst it is
following the plough--all of which points to a relation between the
territory and the fighting. And this view has at least one merit--it
accounts for all the fighting no matter what degree of severity may be
reached or in what way the sexes may be involved. The complexity of the
strife presents no obstacle; for if the biological end of the fighting
is to render the territory, which has already been established, secure
from intrusion, each sex will have its allotted part to play at the
allotted time: thus the battles between the males before females appear
on the scene will decide the initial question of ownership; those
between the females will give an advantage to the more virile members
and insure an even distribution of mates for the successful males; the
constant struggles between paired males will roughly maintain the
boundaries and prevent such encroachment as might hamper the supply of
food for the young; and the co-operation of male and female in defence
of the territory will be an additional safeguard. Each form of battle
will contribute some share towards the main biological function of
reproduction.

Hitherto we have dealt principally with the male. We have referred, it
is true, to the fact that the female co-operates with her mate in order
to drive away intruders, but beyond this, we have made no attempt to
trace what part, if any, she plays in the whole scheme. We must do so
now.

The various steps by which the territory is not only established but
made secure from invasion, imply an inherited nature nicely balanced in
many directions--first of all the male must be so attuned as to be ready
to search for a territory at the right moment; then it must be capable
of selecting a suitable environment; and, having established itself, it
must be prepared to defend its area from a rival, and to resist
encroachment by its neighbours--and if it failed in any one of these
respects, it would run the risk of failure in the attainment of
reproduction. Each individual has therefore to pass, so to speak,
through a number of sieves--the meshes of which are none too
wide--before it can have a reasonable prospect of suc