Here is a curious instance of apparent waste of energy. A pair of Magpies built their nest in an ilex tree. Early one morning there was a commotion in the tree, much flapping of wings and a medley of sounds which told of large birds engaged in a struggle--the Magpies were attacking a pair of Wood-Pigeons. There was no question as to the genuineness of the struggle, nor any doubt as to the proximate end for which the Magpies were striving, for their efforts continued so long as the Wood-Pigeons remained in the tree, and only ceased when they had succeeded in driving them away. Turning next to species which are less distantly related, we find that instances of intolerance are more numerous and that a wider range of species is involved. The hostility that the Lapwing displays towards the Snipe calls for special remark. It often happens that the marshes or water meadows, that are such favourite haunts of the Lapwing, are also resorted to by Snipe for the purpose of securing food, or it may be even for the purpose of reproduction. In such places both species are often abundant; the meadow is divided up into Lapwings' territories, and early in the season the Snipe wander over it in small parties, singly, or in pairs. Now, if it were only on isolated occasions that the Lapwing paid heed to the Snipe, one would not perhaps attach any peculiar significance to the fact; but the pugnacious instinct of the bird responds to the presence of this intruder almost as freely as it does to that of another Lapwing. Again and again, day after day, the Snipe are attacked and driven off in a manner which would be fittingly described as persistent persecution, for the Snipe has neither the physical capacity nor apparently any instinctive tendency to retaliate. Thus a Lapwing may come suddenly upon a small party of Snipe hidden from view in a dyke where they are probing the ground for food; the Snipe immediately rise and fly away and there is momentary confusion as the Lapwing darts first at this one, then at that; or, espying a Snipe at rest at the opposite end of its territory, it will first of all run rapidly towards it, and then fly after it, as, with twisting flight, it darts hither and thither a few feet above the ground; or again, it will attack and rapidly pursue solitary individuals as they skim across its territory and attempt to settle. Is this intolerance merely an exuberant expression of an instinct which is serviceable in another direction? The behaviour of the Lapwing scarcely justifies such a conclusion, for all its actions denote a striving towards some end which we can describe, and it seems to gain satisfaction only when the ejection of the intruder has been accomplished.