strange antics and dances: that a cock partridge, for instance, seems as vigorous as a cock pheasant, and that bright colours and pugnacity are dissociated in such tremendous fighters as the ruff, the coot, and the blackcock. Multiply such instances by the score or the hundred—as can easily be done—and if only the above-stated principle be granted, we get more and more proof of the correctness of a theory to which facts, if dealt with in the more usual way, would be almost instantly fatal. After all, this would be a more satisfactory mode of procedure than that of tolerating a travesty on the strength of a high reputation. There is such a principle in nature as the _lucus a non lucendo_ one, so, as we admit the word mimicry in a false sense—because it is convenient—why not admit that? It would be not one whit less convenient—for the theory. But, handling facts in another way, can we explain the beautiful colours of butterflies as we explain the brilliant plumage of birds—by sexual selection, that is to say? Of this there is not so much direct evidence as could be wished, for butterfly courtship is a long affair, and, for various reasons, is not so easy to watch under natural conditions, as in the case of birds, though this, too, is often beset with difficulties. We know, however, that the male is often much more beautiful than the female, that he pirouettes around her, and that she remains often “icy insensible”—in fact refuses him—which certainly implies a power of choice. Rival males, too, will “whirl round each other with the greatest rapidity, and appear to be incited by the greatest ferocity.”[121] That butterflies, like bees, perceive and are attracted by colours is well known, and it would be strange, indeed, if they were not alive to the many very beautiful and complex patterns on their own wings, when these cannot have been evolved through any principle of protection—since they resemble or suggest nothing—when, in fact, if not beauty, it is difficult to see the object aimed at. Yet the strange suggestion has been made that, though butterflies see colours, they cannot see form, that their sight is defective in some peculiar kind of way. But if form is outline—and if not, what is it?—where is the distinction, seeing that the beginning and leaving off of a colour or of two or more colours must make an outline, and therefore a form? If we see the colours of a pattern where the one ends and the other begins, we see that pattern, and on the other hand, if we could not distinguish one colour from another, or colour from something uncoloured—as, say, the air—we should be blind to colour, as well as to form. Form can hardly be called a thing of itself. It is rather the line of demarcation between two or more things, so that, if each of these is clearly perceived, the form or outline which their juxtaposition makes must be also perceived. Assuming that butterflies see the beautiful arrangements of colour—eyes, spots,