these birds are concerned, there ceases to be a reason for thus, in idea, separating them. Let us see, now, how far this is the case. To begin with these kittiwakes, in their courting, or rather connubial actions on the ledges—as may be seen now, but much more earlier in the year—both sexes open their bills widely, and crane about, with their heads turned toward each other, whilst at the same time uttering their shrieking, clamorous cry. The motion, however, is often continued after the cry has ceased, and this we might expect if the birds took any pleasure in the brilliant gleam of colour which each presents to, and, as it were, flashes about in front of the other. The effect of this it is not easy to exaggerate, and if it is extremely noticeable to an onlooker at some little distance, what must it be to the bird itself, who looks right into the almost scarlet cavity? We have only to think of the inside of some shells, or of a large, highly-coloured flower-cup, to understand the kind of æsthetic pleasure that may be derived from such a sight.
Similar, but much more striking, is the nuptial behaviour of the fulmar petrel. A pair of these birds lying near together, on some ledge or cranny of the rock, will, every few minutes, open their bills to the very widest extent, at the same time blowing and swelling out the skin of the throat, including that which lies between the two sides of the lower mandible, until it has a very inflated appearance. In this state they stretch their heads towards each other, and
