190G.] NKIIVKS OF CiJLAMYDGSELAGTHJS AiXGUmEUS. 977 



liaving a representative of the lingvial branch — i. e., the nei've is 

 continued ventrally on to the pharynx. It should be pointed out, 

 as lierrick justly says (13. p. 324), that as both pre- and post- 

 ti'ematic nerves must originate fi'om the base of the geniculate 

 ganglion, this point of origin cannot be considered a diagnostic 

 feature for the chorda. The remaining conditions, however, are 

 sufficient to determine the chorda,, and agree also with the 

 characters required by Herrick (13. p. 321). 



AUis (1. p. 182 seq.) has discussed the subject generally, and 

 comes to the conclusion that it is still uncertain whether the 

 choi'da is pre- or post-trematic, and tliat the whole chorda litera- 

 ture is in a nebulous condition. With om- ])i'esent knowledge 

 Allis's conclusion cannot be considei-ed justifiable, and for tlu> 

 most reliable conclusions we may still read Herrick (13. p. 316 seq.). 



F. The Oilossophativxgeus. 



The Ninth ISTerve arises from the medulla, by two roots. These 

 roots, of which the cephalad is the smaller, arise in the same 

 vertical plane, but on a lower level than the first large root of the 

 Vagus. This first vagal root is the piincipal lateralis i-oot, so that 

 here, as " in all cartilaginous fish," the ninth nerve " arises from 

 the medulla .... under cover of the anterior rootlets of the 

 lateralis" (3. p. 664). These relative positions are important, 

 because they probably indicate that in origin the latei'alis fibres 

 arise from a segment or segments anterior to that to which the 

 fibi-es of the ninth nerve belong. The cephalad root is motor, the 

 caudad is sensoiy. The latter contains a strand of large medul- 

 lated fibres on its cephalad side, which strand consists without 

 doubt of the lateralis component which passes into the dorsal 

 bi'anch to be desci-ibed later. 



The roots, which soon unite, pass through the chondrocranium 

 by a special foramen. At a distance of 1"5 cm. from the origin, 

 and outside the chondrocranium, the nerve swells into a large 

 ganglion. About halfway between the exit from the brain and 

 this ganglion there apf)eai's on the nerve a somewhat elongated 

 but obvious swelling, from the distal end of which is given off a 

 branch which passes dorsally and somewhat inwards through the 

 cartilage of the cranium. Shortly after entering the cartilage 

 this dorsal bi-anch gives off a fine twig, which passes caudad, but 

 which nnfortunately was not traceable in any case to its des- 

 tination. The main doivsal branch then passes somewhat cephalad, 

 and near the surface of the chondrocranium divides into two fine 

 branches. One of these apparently led to a neuromast, but serial 

 sections would be necessary to definitely demonstrate this. The 

 other branch jji'oceeded to the succeeding neuromast. Transverse 

 sections were made of the dorsal branch of the Glossopharyngeus, 

 and, for comparison, also of the dorsal branch of the Vagus. Both 

 branches were found to consist chiefly of large medullated fibres 



