( 374 ) 
on this subject I shall repeatedly use such figures; here the method 
is applied in order to show the difference in position of the Foramen 
magnum in juvenile and adult skulls. 
In fig. 2 this difference is clearly shown for the skull of Siamanga; 
in the adult skull the Foramen magnum lies considerably more back¬ 
ward than in the juvenile one. At the same time this shifting appears 
to be chiefly caused by lengthening of the basisphenoid and the 
basi-occipitale, the base-length of the Fossa anterior appears in youthful 
individuals to differ little from that in adults. 
The backward shifting of the Foramen magnum causes thesqama 
of the occipital to lose its vaulting for the greater part and to stand 
more vertically. 
After this I may be brief concerning the Anthropoids. OfChimpansc 
I examined two adult and two juvenile skulls, both with the complete 
milk teeth. The basal index of the two former amounted to 65 and 
63, of the two latter to 53 and 50. Also here the the Foramen 
magnum consequently appears to lie fairly considerably more frontally 
in the juvenile skulls. This is moreover shown by fig. 3 in which 
again the mediagrarn of a juvenile skull has been superposed on that 
of an adult one 1 ). For the knowledge of the development of the 
skull it is important to point out that here also the shifting is 
caused by lengthening of the basi-sphenoid and basi-occipital, together 
with an increased steepness of the squama of the occipital. 
That also with Orang the Foramen magnuip is displaced occipital 
is sufficiently proved by comparing the two series of basal indices 
J) I draw attention to the carious section of the palate of the adult chimpanse 
which is thickened and inflated by the right and left sinus maxillaris coalescing 
through the palate, a phenomenon which I also observed in other monkeys (Mycetes), 
