MORPHOLOGY OF THE VERTEBRATE SKULL 21 
(Fuchs had tried to show—’09, pp. 237-242—that the cartilagi- 
nous epiphysis of the mandible was derived from the articular 
portion of Meckel’s cartilage, and that the meniscus represented 
the distal portion of the quadrate, a view which may now be 
regarded as having been thoroughly disproved by Gaupp.) 
7. The connection between the ascending ramus of the dentary 
and the squamosal was at first loose and mobile (Gaupp ’11, 
p. 658). The temporary ‘fixation’ of the dentary upon the squa- 
mosal as a fulerum was effected by the muscles which were in- 
serted on the dentary, serving as ‘active ligaments.’ The new 
joint at first acted only as a force-resolving mechanism (? with 
reference to the direction and strength of the several compo- 
nents of the muscular pulls), while in higher types such as the 
Mustelidae, which have acquired a hinge-joint, motion and the 
direction of pressure are greatly limited. 
8. The increase in size and backward growth of the ascending 
ramus of the dentary and its final contact with the squamosal 
are to be ascribed to three influences or conditions: (a) the gen- 
eral upward and backward trend of the ascending ramus itself, 
which would favor further development in the same direction; 
(b) the progressive diminution of the quadrate, a process which 
may on other grounds be confidently predicated of the ancestral 
mammals; (c) the transformation of the skull as a whole in the 
auditory region (diminution and basal displacement of the audi- 
tory capsule due to the broadening of the brain). As a result 
of these conditions the contact of the squamosal and the dentary 
took place in front of the old quadrato-articular joint, as 1s 
evidenced by the relations of the auriculo-temporal nerve and 
by the detrahens muscle of monotremes (Gaupp ’11, p. 657). 
9. The development of the new jaw articulation must have 
taken place in forms possessing a zygomatic arch such that the 
hinder half was composed of the squamosal (711, p. 657). 
Those who look scornfully at the theoretical deductions of 
comparative anatomy as mere flimsy plausibility, unverifiable 
hypotheses, will doubtless see in Gaupp’s conclusions only a 
confirmation of their sceptical opinions. But those, who by 
patient study succeed in gaining a fair insight into these complex 
