58 THE STRUCTURE OF MAN 
Ecker, this ridge is common in certain races, and it 1s said to be 
homologous with the massive occipital crest of the Apes.’ 
In the normal adult skull the sphenoid appears as a 
single mass, and at a certain age this fuses still further with 
the basioccipital bone. A comparative study of the Mam- 
malian skull, as also an examination of the skull of the 
human embryo, however, shows that the apparently single 
sphenoid represents a series of fused bones. The basal elements 
of the skull are segmentally arranged; but comparison 
with the lower vertebrata shows that this is a secondary 
feature in no way indicative of original metamerism. The 
cranial “segments” are no part of a primordial segmentation 
corresponding with the embryonic somites, as has been clearly 
shown by Van Wijhe and Froriep from the study of develop- 
ment (cf. infra). 
Comparative Anatomy shows us that the orbital and temporal 
fossee were originally one (as they still are even among Lemurs). 
In the human embryo, and even in the new-born child, this fact is 
still indicated by the greater width of the spheno-maxillary fissure, 
the ultimate limitation of which, by extension and the final meet- 
ing of the alisphenoid and the zygoma (malar), is not then 
effected. Before this occurs the frontal and the malar have 
already come into close apposition, and in the double relation of 
the latter to the frontal bone on the one hand and the sphenoid 
on the other, we have a distinctive character of the Primates as 
opposed to all other Mammals. We find, accordingly, that these 
connections are formed very late in the development of Man, as 
compared with the relations of the malar to the maxillary and 
temporal bones, which are established much earlier ontogenetically, 
as they were phylogenetically. | 
Under ordinary circumstances, the upper edge of the ala 
magna of the sphenoid (alisphenoid) reaches the anterior lower 
angle of the parietal, but in rare cases (about 1 per cent of 
European skulls) this junction is prevented by the anterior edge 
of the temporal bone sending out a process to meet the frontal. 
1 (In the Gorilla the sagittal and lambdoidal crests attain so great a develop- 
ment in the male as to give the skull a carnivorous aspect. This feature is an 
accompaniment of the greater development of the temporal jaw-muscles ; and it 
is not acquired by the female. So marked is this sexual difference between the skulls 
of these animals that had they been first found in the fossil state, they would in the 
highest degree of probability have been regarded as at least specifically distinct. We 
have here a most instructive example of an adaptive and secondarily acquired 
character. | 
