412 Journal of Comparative Neurology and Psychology. 



Ichthyopsida is probably found in the r, alveolaris of Urodela" 

 [/our. Couip. Neurol., Vol. XII, p. 269). Hekrick questions 

 whether Strong's r. niandibularis internus in the homologue of 

 the chorda tympani. He finds no nerve in Mcnidia homolog- 

 ous with the chorda tympani, and does not consider the r. pre- 

 trematicus VII to be so homologous because it does not fuse 

 with the r. niandibularis V and hence it does not distribute to 

 the hyoid and mandibular arches in the way characteristic of 

 mammals" {/otir. Conip. Neurol., Vol. IX, p. 324). And 

 finally, in addition to the r. palatinus, r. pre-trematicus and r. 

 post-trematicus, Stannius, as cited by Herkick (loc. cit.) de- 

 scribes in Raja and Spinax another branch of the seventh nerve 

 which fulfills every condition for the chorda tympani. This 

 conflict of opinion shows that the homology of the chorda tym- 

 pani is far from being unquestionably established. 



A chief source of this disagreement lies in the fact that the 

 morphological relations of the chorda tympani to the spiracular 

 cleft throughout the ontogeny of mammals is not completely 

 understood. It has been accepted by leading authorities that 

 the chorda tympani is a pre-spiracular nerve in the mamma- 

 lian embryo. Very recently Herrick in a literary notice of 

 the work by Versluys on "Die mittlere und aussere Ohrsphiire 

 der Lacertilia und Rhynchocephalia" writes: "The detailed 

 descriptions and figures make it very plain that the chorda 

 tympani of reptiles is pretrematic and therefore morphologically 

 pre-spiracular ; and in the absence of very definite proof to 

 the contrary, we must assume the same condition to prevail 

 among the mammals also" i^four. Coinp. Neurol., Vol. XIII, 

 i). Lewis in giving "The Anatomy of a Twelve Milli- 

 meter Pig," says that the seventh nerve "divides into a pre- 

 trematic and post-trematic branch, but the division is under the 

 spiracle or auditory cleft and not over it as in fishes" i^Avi. Jour. 

 Altai., Vol. II, 2). In the last quotation it is not clear, how- 

 ever, whether by "division under the spiracle" it is meant that 

 the chorda tympani itself passes over or under the spiracular 

 cleft. 



In the adult mammal the nerve in question clearly passes 



