Now, as to these eleven thousand, how are they to be divided? To this simple question innumerable answers have been given--it is hardly an exaggeration to say as many answers as there are ornithologists. Every part of the body has had its turn in affording a base for a classificatory scheme. At first, and with the older generation, it was bill and claw; then came a period of bones; later the muscles were held to be all-important; at present the fashion is in favour of taking all characters into consideration, which is clearly a more reasonable way of looking at the matter. The reason for the divergences of opinion--which implies great difficulty in the subject--is that birds are so modern a race. They are now at their heyday of development. By-and-by, when gaps appear in the now serried ranks, classification will be an easier matter; for classification, after all, is an artificial, unnatural sort of thing, if we believe in a gradual modification of species out of pre-existing species. It is not too much to say that, the more perfect our scheme of classification, the greater our ignorance of the group classified. If the only birds known to science were a Hornbill, a Duck, and a Crow, together with a few of the immediate allies of each, we could easily sort them. But there are so many intermediate forms which absolutely decline to fit accurately into any system. Then the would-be systematist has to distinguish between those characters which imply a deep-seated relationship and those which are only due to similar needs. The aim of classification is, of course, to indicate real relationship, not merely to pigeon-hole in a convenient way. Real relationship is often masked by superficial differences. For instance, the common blindworm of our hedgerows is not, as might be thought, a snake, but a lizard; it appears to be unlike the lizard in having no legs, and to be so far a snake. Indeed, the terror inspired by this peaceful reptile must stand it in good stead with any except human foes. But its whole anatomy is built upon the lizard, and not upon the snake, plan. We disregard, therefore, in a scheme of classification the likeness to a snake, remembering that in Nature, as in morals, appearances are apt to be deceptive. The owls, among birds, are believed by many to offer an instance of the same kind of deception. By all the older systematists, and by many of the more modern, they are placed with the hawks in one group. No doubt the owls bear a certain likeness to the hawks. They have formidable claws and a hooked and powerful beak; they kill their prey; and only differ superficially in that they love the darkness, while the hawks hunt by day. Now, in certain details of anatomy, particularly in the windpipe and the muscles, the owls are much more like that division of birds which includes the goatsuckers. The mention of this latter family brings us face to face with another difficulty. If the superficial