592 'Journal of Comparative Neurology and Psychology. 



terior wall and extends over the dorsal and ventral walls; conse- 

 quently the posterior branches of each branchial nerve carry 

 many more motor fibers than the anterior branches. In the case 

 of the VII nerve there is no gill sac in front of it to be innervated, 

 but it sends one motor branch forward which goes ventro-mesad 

 in a thick muscle (fig. lO, m.h-h.a.) which with its fellow forms 

 a shng depending from the cornual cartilages, in which the front 

 end of the circular muscle of the "tongue" rests. This is the m. 

 hyo-hyoideus anterior of P. Furbringer which he states is inner- 

 vated by the internal ramus of the maxillaris. This muscle 

 appears to the writer to be much less closely associated with the 

 large circular muscle of the tongue (hyo-hyoideus posterior) than 

 Furbringer's account implies. It would seem to have a special 

 function to raise the tongue during the rasping and sucking move- 

 ments. The fact that it receives its innervation from the VII 

 nerve is stronger evidence against its being considered a part of 

 the circular muscle, which is innervated by the trigeminus. 



It was pointed out in a previous paper (1905) and was already 

 clear from the descriptions by P. Furbinger that the trige- 

 minus of cyclostomes is peculiar in that the maxillary ramus con- 

 tains motor fibers. The maxillaris indeed innervates the majority 

 of the muscles connected with the whole buccal apparatus and P. 

 Furbringer failed to recognize a ramus mandibularis, assigning 

 all branches below the ophthalmic ramus to the maxillaris. This 

 was an error. I have shown in the general description above that 

 a pure motor component of the trigeminus can be distinguished 

 in the root and ganglion by its compact rounded form and the 

 coarseness of its fibers. This bundle supplies the internal and 

 external velo-hyomandibular muscles and the protractors, retrac- 

 tors and circular muscle of the tongue. Now if the lingual appa- 

 ratus corresponds to the lower jaw of higher forms, it is proper 

 to consider this nerve homologous with the motor part of the 

 mandibular ramus of true gnathostomes. 



Although my preparations leave some uncertainties, all the 

 other muscles about the buccal and mouth cavities seem to be 

 innervated by branches of the maxillaris. 



My preparations are not suitable for the reconstruction of the 

 muscles and I will not attempt any further description of the 

 muscles and their innervation or discussion of their action. I 

 am convinced, however, that in many respects Furbringer's 



