272 



barbel of Siluroids". In Silurus glanis, however, I find not only a 

 maxillary tentacle, but also what appears to be a maxillary fold, the 

 tentacle apparently being a special development of the anterior portion, 

 only, of the otherwise fairly normal fold. That this tentacle of Silurus 

 is a homologue of a part, at least, of the maxillary fold of Amia is 

 shown by the innervation (No. 2, p. 635), and it may be here stated 

 that the fold in the upper lip of Polypterus is innervated by a nerve 

 that runs backward in it in a position analogous to that of the maxillary 

 branch of the Ramus maxillaris superior trigemini of Amia. This nerve 

 in Polypterus I have not yet traced to its origin, but it is probably 

 the homologue of the nerve of Amia, for Pollard shows no recurrent 

 branch related to the inner surface of the so-called maxillary bone of 

 the fish. This nerve in these two fishes seems certainly the homologue 

 of the terminal part of the infraorbital nerve of man, and the relation 

 of the nerve, in man, to the superior maxillary bone is that of the 

 nerve to the so-called maxillary bone of Polypterus, and not that of 

 the nerve to the maxillary of Amia, 



In Gadus there is a nerve that traverses the maxillary fold of the 

 fish and then passes downward around the angle of the mouth into 

 the mandibular fold, thus having, in its course, the relation to these 

 two folds that a branchial nerve has to its arch. The terminal 

 distribution of this nerve was established some time since, when I 

 was working on Gadus, but as that work was discontinued I do not 

 know its deeper origin. 



The prepalatine piece of Pollard's descriptions of Siluroids is 

 not considered by him, as I understand him (No. 33, p. 407), as the 

 homologue of Sagemehl's submaxillary cartilages (No. 37, p. 101), 

 although to me these several structures seem strictly homologous. 

 Sagemehl considered his submaxillaries as the homologues of the 

 upper labials of Selachians; while Pollard considers these labials as 

 the homologues of the premaxillary, maxillary and coronoid tentacles 

 of Siluroids, the prepalatine piece being the "root piece of a tentacle", 

 but originally continuous with the skull cartilage. The distinction be- 

 tween the prepalatine piece and the related tentacle itself is not here 

 clear, excepting by reference to his descriptions of Auchenaspis. The 

 ossification of the prepalatine piece in that fish seems to correspond 

 to the septo-maxillary of Amia, and the piece seems simply to give 

 articulation to the maxillary bone and the tentacle that that bone bears. 



The tentacles of fishes are, as is well known, sensory structures, 

 the organs that give them their sensory qualities being always, so far 

 as I can find, of the class called by Merkel terminal buds. These 



