different forms is properly brought out. Without my seeking it, the list includes the two extreme forms, as I believe them to be, of dark and light; the former represented by a uniformly dark-brown bird, the latter by one having the whole under surface of the body, as well as the sides and nape of the neck, of a beautiful cream colour, by virtue of which, and of the salient contrast exhibited between this and the dusky upper surface, it is extremely handsome, not to say beautiful—one of the handsomest of all our birds in my opinion. Both the extreme forms are uncommon, but only, I think, as compared with all the intermediate shades, not with any one of them. Also the extreme light, or handsome, form seems to me to be commoner than the extreme plain one. Should not a bird like this be described as multimorphic rather than as dimorphic? I believe that there exists as perfect as series between the two extreme forms as between the least eye-like and the most perfect eye-feather in the tail of the peacock—to take the well-known illustration given by Darwin to enforce his arguments in favour of sexual selection. The eye, however, insensibly masses the less saliently distinguished individuals together, so that those in whose plumage the light colour is more en évidence than the dark, go down as the light form, and vice versa. Moreover, the more prononcé a bird is, in one or another direction, the more it is remarked; so that, perhaps, the intermediate shadings are forgotten, on the same principle as that by which extreme
