22 HAV. [Vol. IV. 



bone running its length ; and an examination of the adult at 

 hand shows that the cartilage is only partly ensheathed by bone. 



The lower end of the first branchial arch is meanwhile under- 

 going ossification of a different kind, being overlaid, as before 

 mentioned, with bone deposited ectosteally. 



To the foregoing on the cartilaginous and bony skull, I make 

 the following notes on other structures belonging to the head : — 



The common ganglion of the facial and auditory nerves lies 

 wedged in between the otic capsule and the outer bar of the 

 basicranial cartilage. It gives origin, as usual, to the facial 

 nerve, which runs outward to escape by the facial foramen, and 

 to the auditory, which enters and supplies the anterior portions 

 of the labyrinth. Further back the ganglion, or what appears 

 to be a portion of it, seems to be crowded through the mesial 

 wall of the capsule so as to appear to lie partly within the cap- 

 sule. Here it lies in close relation with the mesial wall of the 

 sacculus, to which it distributes nerve-fibres, as it does also 

 probably to the rudimentary cochlea. This branching of the 

 auditory nerve before it enters the capsule I have observed also 

 in Aniblystoma and Spelerpes. The acoustic nerve in the frog 

 enters the labyrinth by two or more foramina (Owen, Anat. 

 Vert., Vol. I, 312). 



The facial nerve, after emerging from the cranial cavity, 

 courses outward and passes below the columella. My sections 

 show this plainly. Dr. Wiedersheim undoubtedly errs when he 

 announces {op. cii., p. 137) the rule that the facial nerve in all 

 Urodeles, without exception, makes its way out over the suspen- 

 sorio-stapedial ligament, whether this consists of fibrous tissue 

 or cartilage. And unless the relation of the facial nerve to the 

 columella in Meiwpoma is variable, it, too, offers an exception 

 to his rule, despite the figures which he gives to illustrate these 

 parts {Kopfskcltt, etc.. Fig. 24). Messrs. Parker and Bettany 

 {Morphology of the Skull, p. 132) state that the cartilage pass- 

 ing between the stapes and the suspensorium lies over the facial 

 nerve, and a dissection made by myself is confirmatory of this 

 statement. 



Mention has already been made of the foramen of the ductus 

 endolymphaticus. This latter is a narrow tube which enters the 

 brain-cavity, having taken its origin in the sacculus. On the 

 upper and outer surface of the brain it expands into a saccus 



