58 THE STRUCTURE OF MAN 



Ecker, this ridge is common in certain races, and it is said to be 

 homologous with the massive occipital crest of the Apes. 1 



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 

 fossse 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.] 



