tions as they arose. Now some may think that the theory
would be more likely to be true if the territory had but one purpose to
fulfil, and that one the same for every species; and they may see
nothing but weakness in the multiplication of ways in which I shall
suggest it may be serviceable. But such an objection, if it were raised,
would arise from a mistaken conception, a conception which, instead of
starting with a relationship and working up to the "territory," sees in
the "territory" something of the bird's own selection and thence works
back to its origin. Holding the view that it is nothing but a term in a
complex relationship which has gradually become interwoven in the
history of the individual, I see no reason why the fact of its serving a
double or a treble purpose should not be a stronger argument for its
survival. I now propose to examine the various ways in which the
territory may have been of use in furthering the life of the individual,
and the circumstances in the inorganic world which have helped to
determine its survival.

The purpose that it serves depends largely upon the conditions in the
external environment--the climate, the supply of food, the supply of
breeding-stations, and the presence of enemies. Hence its purpose varies
with varying conditions of existence. But before we proceed to examine
the particular ways in which it has been modified to suit the needs of
particular classes of species, and the reason for such modifications, we
must inquire whether there is not some way in which it has been
serviceable alike to every species, or at least to a large majority of
them.

Success in the attainment of reproduction depends upon the successful
discharge of the sexual function; and the discharge of the sexual
function depends primarily upon an individual of one sex coming into
contact with one of the opposite sex at the appropriate season and when
its appropriate organic condition arises. Now the power of locomotion is
so highly developed in birds that it may seem unreasonable to suppose
that males and females would have any difficulty in meeting when their
inherited nature required that they should do so, still less reasonable
to suggest that this power might even act as a hindrance to successful
mating. Nevertheless, if we try to picture to ourselves the conditions
which would obtain if the movements of both sexes were in no wise
controlled, and mating were solely dependent upon fortuitous gat