DAVID HEPBURN. [No. 3. 



of Ihe young Chimpanzee will show that in the young state their 

 proportions are considerably nearer to those characteristic of 

 the adult Man than they are found to be in the adult Chim- 

 panzee. This fact was so unexpected and so surprising that it 

 determined me to examine a number of fætal and young 

 British skulls in order to ascertain the proportions of their præ- 

 and post-condyloid segments. Only one of these skulls possessed 

 erupted teeth, the others being fætal or under the age for the 

 appearance of teeth. In those skulls without teeth an un- 

 expected variation was found, but in every one the postcondyloid 

 segment was the larger, varying from 50.8 to 60 per cent. of the 

 glabello-occipital diameter. In the skull with teeth (the second 

 permanent molar was not erupted) the postcondyloid segment 

 constituted 56.1 per cent. of the total diameter. 



It is quite clear therefore that in the young human skull as 

 in the young Chimpanzee, the postcondyloid segment is much 

 larger than it is afterwards found in the adult state. 



Now if adult skulls only were examined, we should conclude 

 that the occipital condyles were developed farther forwards upon 

 the base of the skull in a series which presented the Gibbon at 

 one end and the brachycephalic Scandinavian at the other. 

 When however we turn to the fætal and young skulls, we find 

 that the very opposite is the explanation and that the occipital 

 condyles retreat steadily backwards in relation to their ultimate 

 position below the glabello-occipital diameter. Indeed it becomes 

 a question of the distance to which they are to be transferred 

 backwards. Oi: course we recognise that they do not change 

 their actual position upon the occipital bone and therefore this 

 fact may be expressed by saying that the cranial box with the 

 contained brain is tilted or rotated forwards during its growth 

 and progress towards the adult state, so as to augment the 

 præcondyloid segment and correspondingly diminish the post- 

 condyloid segment. The measurements given in the Table show 

 that this change occurs to a greater extent in the skulls of 

 savages than among those of civilised men, even when the skulls 

 belong to the same index-group; and if one may judge from the 



