injury inflicted. It is necessary to bear this in mind, because it is held by some, who have carefully observed the actions of various species, that overmuch importance is attached to the conflicts, that in a large number of instances they are mere "bickerings" and lead to nothing, and that they are now only "formal," which means. I suppose, that they are vestigial—fragments of warfare that determined the survival of the species in bygone ages. But if the conclusion at which we have just arrived be correct, if we can recognise a single aim passing through the whole of the warfare—and that one the removal of an intruder from a certain position, then we need no longer concern ourselves as to the degree of severity of the battles—we see it all in true perspective. Neither exhaustion nor physical inability are the sole factors which determine the nature and extent of the fighting; there is a more important factor still—position. According, that is to say, to the position which a bird occupies whilst fighting is in progress, so its pugnacious nature gains or loses susceptibility, and it is this gain or loss of susceptibility which I refer to when I speak of the fighting as being controlled.
What we have then to consider is the relation of "susceptibility" to "position." We can explain the relationship in two ways. We can say that the part of the nature of the male which leads to the occupation of a territory, and is partly hereditary and partly acquired, is stronger than the part which leads the bird to fight, and
