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muscle segment, and turns backward internal to the skin. It here 

 immediately encloses an artery (Fig. 1), the nerve thus, in this, as also 

 in its general appearance, resembling exactly the buccalis and ophthal- 

 micus lateralis. It is undoubtedly of the same sensory character as 

 those two nerves, whatever that character may be, and, from its origin 

 and general course, it might be the homologue either of the oticus 

 facialis, of the lateral sensory branch of the glossopharyngeus , or of 

 the linea lateralis vagi of the gnathostome Ichthyopsida. I take it, 

 as already stated, to be the latter nerve. It is certainly not in any 

 way a branch of the nerve that I have described as the buccalis late- 

 ralis, as the oticus usually is of the buccalis facialis, but it appears, 

 in dissections, as an apparent branch of that nerve. It may therefore 

 be the oticus facialis of von Kupffer's descriptions, the dorso-posterior 

 root of the maxillo - mandibularis ganglion, plus this root, then being 

 the root of von Kupffers ganglion C. But it seems more probable 

 that it is either a root not found by von Kupffer, or mistaken by 

 him as one of the two roots he ascribes to the acusticus ; the character 

 of its ganglion cells being in favour of this latter supposition, and not 

 of the former one. 



Vagus and First Spinal Nerves. 



These nerves can not be satisfactorily traced in any of my series 

 of sections, and they are referred to here simply because of the bearing 

 that certain of their branches have on my interpretation of the skull. 



The roots of the vagus could not be determined. The nerve, how- 

 ever, arises as two bundles of fibres, which run downward and back- 

 ward close together, and pierce the membranous side wall of the cra- 

 nium opposite the hind end of the otic capsule. The two bundles then 

 unite to form a single nerve trunk, which runs backward across the 

 dorsal surface of the cartilage that connects the hind end of the otic 

 capsule with the parachordal cartilage. The nerve then passes across 

 the dorsal surface of the m. cranio - hyoideus, which muscle has its 

 origin in part from the hind end of the same cartilage, and beyond 

 that muscle the nerve continues backward about midway between the 

 notochord and the superior lateral cartilage. There it soon passes 

 onto the dorsal surface of what Müller calls the second division of 

 the constrictor oesophagei, which muscle, and also the third division 

 of the same muscle, it is said by Müller to innervate. This I could 

 not control. A branch is here soon given off, on the lateral aspect of 

 the main trunk, and this branch soon becomes ganglionic, the main 

 nerve containing no ganglion cells up to this point. The ganglionic 



