upon it. It would be useless for an individual to be pugnacious if it had no fixed abode; equally useless for it to establish itself on a particular ledge if it had no power to defend it—all of which implies an inherited nature similar to that of the Bunting. But the proximate end to which the competition is directed is not alike in the case of both species. In the case of the Guillemot it has reference solely to the piece of rock whereon the egg is laid; in the case of the Bunting to a piece of ground capable of furnishing an adequate supply of food for the young; and the reason for the difference is this, that there is always an abundance of food in the water beneath the cliff, but breeding stations are scarce, whereas there is always an abundance of situations in the marsh in which the Bunting can place its nest, but the supply of food varies and at times can only be obtained with difficulty.
If then the Guillemot were to behave after the manner of the Bunting and assign to itself a portion of the face of the cliff, or if it were only to occupy a few ledges, or an even lesser area—a single ledge—what would be the result? That it would attain to reproduction is beyond question; that the egg would be safely deposited there can be no manner of doubt j neither is there any reason to suppose that the offspring would not- be successfully reared. But, indirectly, its behaviour would affect the Guillemot race. For if it be true, as the crowded ledges certainly seem to show, that there is a dearth of
