No. 387.] THE OSSICULA AUDITUS. 225 
of these homologies — the incus-quadrate homology — is that it 
must necessarily follow that the articulation of the lower jaw 
with the cranium in the mammals cannot be homologous with 
the articulation in the lower vertebrates, and that it is difficult 
to imagine this transfer of functions from one point to another. 
The weight of this objection we admit, but we shall endeavor 
to show a little later that no matter what view one takes of the 
fate of the quadrate in the mammals,.there is this same problem 
of the formation of a new articulation to be met, for it is 
impossible, upon any basis, to homologize the articulation of 
the lower jaw in the mammals and the non-mammalian groups. 
Fic. 3. — Diagram of otic region in pig embryo: a, grey of external meatus; c, body of mal- 
a nri ct, chorda tympani; /, facial nerve ; A, hyoid; #, Meckel’s cartilage (processus 
gus); #2, manubrium mallei; g (č), nae aaa i * Pap sh, styloid process of 
aa sm, stapedial muscle ; sf, stapedia 
In all ichthyopsida and sauropsida the articulation of the 
lower jaw with the cranium is in reality an articulation between 
the quadrate and Meckel’s cartilage, and even when it becomes 
an osseous articulation it is an ossification of the cartilages 
which affords the articular surfaces. In the mammals, on the 
other hand, Meckel’s cartilage does not approach in any way to 
the glenoid fossa. The mandible forms around the distal portion 
of Meckel’s cartilage as a membrane bone, and its ascending 
ramus grows away from the cartilage towards the glenoid fossa. 
So it is evident that the mandibular part of the articulation in 
the mammals is not formed by the Meckel’s cartilage. How 
about the fusion of the quadrate in the squamosal, as maintained 
by Peters, Albrecht, and Cope? Development shows us not 
the slightest trace of cartilage in the region of the squamosal ; 
