CEPHALISATION.—Such is the name given by Prof. Dana to what he terms a fundamental principle in the development of the system of animal life. Its meaning can be best explained by the employment of the instances used by its author. The lobster and the crab are closely allied decapod crustaceans. In the lobster the tail is large, the cephalo-thorax elongate, and the antennæ of considerable size. In the crab the tail is minute, packed under the cephalo-thorax, which is short, as are the antennæ; and from this we may infer that passing upwards from the Macrural to the Brachyural forms there is an abbreviation and a compacting of structure before and behind the head. “In the whale the tail is the propelling organ and is of enormous power and magnitude, and the brain is very small and is situated far from the head extremity in a great mass of flesh and bone furnished with poor organs of sense.” The principle is therefore that in low types “there is, usually, large size and strength behind, an elongation of the whole structure, and a low degree of compactness in the parts before and behind; in the high, there is a relatively shorter and more compacted structure, a more forward distribution of the muscular forces or arrangements, and a belter head.” The analogy is ingenious, but we can see nothing of value in the argument more than a repetition of the well-known principle that height in the scale of creation and amount of cerebral development are correlated phenomena. Are we to place the koala, which, by the way, is wonderfully like some of the much higher Lemurs in its proportions, at the top of the Marsupial phyllum and the kangaroos at the bottom, because the former wants the tail and has a blunt nose, whilst the latter have an enormous caudal appendage and a slender snout? Is the sun-fish so much higher than the eel, and the ostrich than the lyre bird? We fear that cephalisation is not a true law of nature.