an individual, when in company with the flock, may be called upon to endure, its customary hostile response will fail to be elicited. An incident which happened in the spring of 1917 will serve to make this clear. A flock of some thirty Yellow Buntings. Greenfinches, and Chaffinches were feeding in one corner of a field which had recently been sown with barley. As they sought their food they wandered outwards into the middle of the field, and in so doing, passed across the territory of a Skylark. Whereupon the Skylark became excited, uttered its call-note rapidly, and rising a few feet from the ground, attacked those members of the flock that were nearest, which happened to be the Yellow Buntings; and so determined were its onslaughts that the Yellow Buntings were forced to retire. The Skylark showed no discrimination as to sex, but attacked both males and females, and within a few minutes succeeded in driving away at least two pairs. One would have expected that the Yellow Buntings would have made some show of resistance; one would have thought that the fact of being violently attacked would have supplied a stimulus sufficiently strong to evoke a corresponding hostile response: yet there was no mistaking the lack of interest that they displayed in the contest—they made no effort to retaliate but seemed to accept the situation as unalterable and left.
So far we have examined only those cases in which the pugnacious instinct was stimulated in
