nd. But I have already drawn
attention to the fact that, so long as a definite result is attained,
the severity of the struggle and the amount of injury inflicted are
matters of small moment. Let us, however, run over the substance of the
argument, and then briefly refer again to this point of view.

After enumerating instances of hostility, sufficient in number, so it
seemed, to constitute reasonable ground for the belief that they had a
part to play in the life-history of the individual, the two questions we
set ourselves to examine in this chapter were: Is there any circumstance
in the life behaviour of the individual with which the hostility can be
definitely related; and, will the hostility lead to the securing of a
greater measure of success in the attainment of reproduction?

Many different species assemble together in winter and roam from place
to place in search of food. But in spring their behaviour undergoes a
remarkable transformation; they avoid one another and become
quarrelsome, so much so that whereas the outstanding feature of the
winter is sociability, that of the spring is hostility. With this
general fact before us, we proceeded to investigate this change of
behaviour still further. First of all we took the case of a migrant,
and, comparing its behaviour, as it journeyed, with that when finally it
reached its destination, we found that the bird which was notoriously
pugnacious when in occupation of a territory betrayed no interest in
other species as it travelled to the accustomed breeding ground. Not
only so, but even though it was attacked, we found that its pugnacious
instinct still failed to respond. Here, however, it may be contended,
and with reasonable justification, that in the interval which elapses
before the ultimate destination is reached, some change in the organic
condition of the bird may occur which will account for its altered
behaviour; or, it may be urged, with no less justification, that whereas
on migration the bird is unpaired, when the destination is reached it is
probably in possession of a mate and is therefore quarrelsome. Now, at
the most, the interval can only be a matter of a few days, and it is
unlikely that organic changes sufficient to bring about so important an
alteration of behaviour could occur in so short a time, still less
likely that they could be timed to come into functional activity just at
the moment when the bird reaches its breeding ground. And with regard