have only had the time, or the patience, to note down fifteen, which I did very carefully, through the glasses, as the birds stood amidst the short heather on the ness-side. Here they are; not, perhaps, very precisely or scientifically defined, but none the less truthfully so, for all that, and as accurate, I think, as the fact that no two people see colours quite alike will allow. But they, at any rate, bring out four facts, which, together, have, I think, a distinct meaning, viz. (1) the unmistakable and, for the most part, pronounced difference in these fifteen forms of a two-formed species; (2) the likeness of the extremely plain, permanent form to the plain-coloured great skua; (3) the same resemblance in the first true plumage of the young bird; and (4) the absence in the young bird of the two lance-like feathers which, in the old ones, project beyond the rest of the rectrices, but which are also absent in the great skua. Well, here they are.
(1) The neck, from just below the head, with the throat, breast, and ventral surface, as far as the legs, a beautiful creamy white; the rest dark, as in the ordinary dark form, but I was not careful to note the precise shade; the crown of the head—and this, it seems, is universal—sufficiently dark to appear black. This bird represents, I think, the extreme of the light or ornate form, in which dark and light are almost equally divided.
(2) The light colouring extends, speaking roughly, over the same parts, but is very much less bright and pure. It might be described as a dun-cream or cream-
