Now, collections of the skulls of criminals comparatively often contain skulls with a cubic capacity of less that 1,100 c.c., whereas skulls as small as this are hardly ever met with in collections of normal skulls; skulls ranging in cubic capacity from 1,100 c.c. to 1,800 c.c., which in collections of normal skulls are found to the extent of from 6 to 10 per cent., in collections of the skulls of criminals have been present, in various instances, to the extent of 17·8, 18, 65·5, and 72·2 per cent. respectively. Skulls below the normal mean in cubic capacity, which in collections of ordinary skulls are present to the extent of from 25 to 30 per cent., are found in the different collections of the skulls of criminals to be present to the extent of from 30 to 60 per cent. To put the matter in a word, the criminal’s skull is often submicrocephalic; it is, however, necessary to point out that skulls with the very largest cubic capacity, exceeding 1,600 c.c., are met with twice or thrice as often among the skulls of criminals (although this is not true of the Italian collections personally known to me) as they are among bone-dealers’ or museum skulls. A somewhat similar characteristic is exhibited by all the criminal characters accessible to measurement. When the material under investigation is derived indifferently from the general population, the extreme values recorded by measurement are seldom encountered. Among criminals, on the other hand, these extreme values occur much more frequently; and, indeed, the extremely _low_ values are encountered in criminals with especial frequency when the dimension under consideration is one which usually increases as we pass from lower to higher stages in the scale of development. For example, great breadth of the face across the zygomatic arches is a characteristic of lower development; in criminals (900 instances), exceptional width and exceptional narrowness of the face in this region occurs more frequently than in the general population; but this is true to a greater extent as regards the maximal than it is as regards the minimal values of this dimension of the criminal skull.