The extent to which abnormal conditions of life are capable of modifying the shape of skulls may be gathered from the comparison of the skull of an Irish hog with that of its ancestor the wild-boar, or even that of a hyæna kept in confinement with that of a wild animal of the same species. (See Osteol. Series, Brit. Mus.) _The British Dolicho-cephali and Brachy-cephali._ The materials for working out the craniology of Europe, in prehistoric times, do not justify any sweeping conclusion as to the distribution of the various races, but those which Dr. Thurnam (_op. cit._) has collected in Britain offer a firm basis for such an inquiry. In the numerous long barrows and chambered “gallery graves” of our island, which from the invariable absence of bronze, and the frequent presence of polished stone implements, may be referred to the neolithic age, the crania belong, with scarcely an exception, to the first two of these divisions. In the round barrows, on the other hand, in which bronze articles are found, they belong mainly to the third division, although some are ortho-cephalous. Sometimes, as in the case of Tilshead, the crania in the primary interment, over which the long barrow was raised, are long, while those in the secondary, which have been made after the heaping up of the barrow, are broad. On evidence of this kind Dr. Thurnam concludes, that Britain was inhabited in the neolithic age by a long-headed people, and that towards its close it was invaded by a bronze-using race, who were dominant during the bronze age. This important conclusion has been verified by nearly every discovery which has been made in this country since its publication. The long skulls graduate into the broad, the oval skulls being the intermediate forms; and this would naturally result from the intermingling of the blood of the two races. There may, however, have been a tendency towards ortho-cephalism in the dolicho-cephali, without any admixture of foreign blood, since absolute unity of form could not be expected.