114 ANIMAL LIFE AND HUMAN PROGRESS 



roological type, definitely established at a period in which the 

 embryo was held to display perfectly generalised mammalian 

 characters. 



A host of other features in the skull present themselves in 

 the train of this question of the premaxillary bone. In Man 

 the nasal bones remain separate, as a rule, throughout life, but 

 in monkeys and anthropoid apes they are greatly reduced 

 elements, and they are frequently fused together into a single 

 bone before the animal is born. In this very characteristic 

 feature Man is considerably more primitive than are the 

 monkeys. Again, the bones which form the floor of the cavity 

 of the skull show a strange contrast as between Homo and all, 

 save two, representatives of the Anthropoidea, for whereas 

 in Man the primitive arrangement, by which the mesethmoid 

 articulates on the floor of the skull with the pre- and orbi to- 

 sphenoid, is universal, in the monkeys and anthropoid apes 

 a large bilateral ingrowth of the frontals separates these two 

 elements. The arrangement of the bones of the cranial wall 

 at the point known as the pterion is a more complex problem, 

 but nevertheless it constitutes a distinction between the human 

 and monkey skull which cannot be ignored, even if its signifi- 

 cance is so far rather uncertain ; and here again the human 

 type is the simpler and more primitive one. Again, the late 

 persistence, and not infrequent permanent persistence, of 

 the separation of the two frontal bones at the metopic suture 

 is a human feature which is not shared by the monkeys 

 or anthropoid apes. Many authorities regard the human 

 persistence of the metopic suture as a secondary feature re- 

 acquired under especially human conditions of brain develop- 

 ment. This may indeed be the case ; but it is at any rate 

 a primitive mammalian feature, and since so many such 

 features are present in the human skull, and serve to dis- 

 tinguish it from that of the monkeys and apes, good proof of 

 its secondary nature is needed for the acceptance of this 

 belief. 



Passing over many far less conspicuous, but still by no 

 means unimportant points in which the human skull differs 

 from that of the rest of the Primates, we may note one other 



