degree, to this revolution of the side and roof bones of the
skull upon the basicranial axis observed upon so great a scale in the
mammalian series? Numerous observations lead me to believe that we must
answer this question in the affirmative.

The diagrams in Figure 29 are reduced from very carefully made diagrams
of sections of four skulls, two round and orthognathous, two long and
prognathous, taken longitudinally and vertically, through the middle.
The sectional diagrams have then been superimposed, in such a manner,
that the basal axes of the skulls coincide by their anterior ends, and
in their direction. The deviations of the rest of the contours (which
represent the interior of the skulls only) show the differences of the
skulls from one another, when these axes are regarded as relatively
fixed lines.

The dark contours are those of an Australian and of a Negro skull: the
light contours are those of a Tartar skull, in the Museum of the Royal
College of Surgeons; and of a well developed round skull from a cemetery
in Constantinople, of uncertain race, in my own possession.

It appears, at once, from these views, that the prognathous skulls, so
far as their jaws are concerned, do really differ from the orthognathous
in much the same way as, though to a far less degree than, the skulls
of the lower mammals differ from those of Man. Furthermore, the plane
of the occipital foramen ('b c') forms a somewhat smaller angle with the
axis in these particular prognathous skulls than in the orthognathous;
and the like may be slightly true of the perforated plate of the
ethmoid--though this point is not so clear. But it is singular to remark
that, in another respect, the prognathous skulls are less ape-like than
the orthognathous, the cerebral cavity projecting decidedly more
beyond the anterior end of the axis in the prognathous, than in the
orthognathous, skulls.

It will be observed that these diagrams reveal an immense range of
variation in the capacity and relative proportion to the cranial axis,
of the different regions of the cavity which contains the brain, in
the different skulls. Nor is the difference in the extent to which the
cerebral overlaps the cerebellar cavity less singular. A round skull
(Figure 29, 'Const'.) may have a greater posterior cerebral projection
than a long one (Figure 29, 'Negro').

Until human crania have been largely worked out in a manner similar to
that here suggested--until it shall be