402 PROF. HUXLEY ON THE REPRESENTATIVES OF [May 27, 
remains for a time, as Meckel’s cartilage, but soon disappears. The 
ramus of the mandible of a Mammal, therefore, cannot contain any 
representative of the os articulare of the Sauropsidan, which takes 
its origin in the proximal end of Meckel’s cartilage. 
The tympanic bone of the Mammal is developed, quite indepen- 
dently of the cartilaginous axis of the first visceral arch, in the 
fibrous rim of the tympanic membrane. Therefore it cannot repre- 
sent the Sauropsidan quadrate, which is preformed in cartilage, and 
is, in fact, the proximal end of the cartilaginous axis of the first 
visceral arch. 
These arguments, to my mind, retain their full force, and have 
not been affected by the observations of Prof. Peters. 
In the next place, it is not disputed that the malleus of the Mammal 
arises by the direct ossification of a part of the cartilage of the first 
visceral arch. But I have shown, in the present paper, that the supra- 
stapedial of the Sauropsidan is the proximal end of the hyoidean, 
or second, arch. It is therefore impossible that the suprastapedial 
should be, as Prof. Peters supposes, the homologue of the malleus, 
Fig. 6. 
AY 
HNN 
Ms \ 
4 yh 
M Wy 
The ear-bones and the adjacent parts (the tympanic membrane, the tympanic bone 
of the squamosal, and the ramus of the mandible being removed) of a human 
foetus at about the 5th month. Magnified four diameters. 
T.t. The tegmen tympani, part of the periotic mass. MM. The malleus, with its 
Folian process (Pg) passing into Meckel’s cartilage. JZ. The incus. S¢. 
The stapes, with the cartilaginous process @, which extends {rom the region 
of the orbicular bone into the stapedius muscle, Sip. St.h. The stylo-hyal 
or styloid process, still quite cartilaginous. jr, The foramen rotundum. 
