121 



in Selachiaus and in Protopterus. In both cases they are nearly always 

 connected with the brain close to the lamina terminalis. 



Sewertzoff^), in 1902, described a similar nerve in embryos in 

 Ceratodus, thus making its presence known in another one of the 

 Dipnoi. The most interesting point which he adds to the observations 

 of PiNKUS is that it is ganglionated. As to peripheral distribution, it 

 ends in the mucous membrane of the anterior nasal chamber — not in 

 the sensory epithelium. Sewertzoff apparently overlooked my paper 

 in the Anatomischer Anzeiger with its figures, and its reference to 

 the observations on this nerve, by Pinkus and Allis. 



It may be remarked, in passing, that my paper referred to, was 

 the first one to point out a ganglion on this nerve in any animal, and 

 to give an account of its embryonic history. 



I have had (also through the kindness of Dr. Dean of Columbia 

 University) the use of an adult specimen of Ceratodus. The con- 

 dition of the brain did not permit of any critical observations, but 

 I readily located the nerve, and its ganglion, near the anterior border 

 of the prosencephalon. Just back of the ganglion was a relatively 

 short root joining it to the brain, within the furrow, on the ventral 

 side, as indicated by Sewertzoff. In the adult the elongated tractus 

 is formed, and the nasal cup removed a considerable distance in front 

 of the brain, so that, the ganglion observed is not in the same re- 

 lative position that Sewertzoff has shown it to be in the embryo. 

 The nerve in Ceratodus is apparently attached to the brain much 

 further forward than in Protopterus. 



PiNKUS had pointed out the close position of this nerve to the 

 recessus praeopticus, and Sewertzoff proposes for it the name of 

 "Nervus praeopticus", but in view of its dorsal position on the brain 

 in forms like Raja, Trygon, and Myliobatis, the name does not seem 

 to me applicable. 



In my paper of 1899^) I suggested in a tentative way calling it 

 "accessory olfactory" in the following words: "On account of its close 

 relation with the fibers of the main olfactory and to the nasal mem- 

 brane, it is best for the present to refer it to the olfactory system, 

 and, perhaps, te designated it 'accessory olfactory'". But that name 

 is objectionable, since it prejudices the question of its function. 



This nerve arises on the morphological tip of the primary fore- 

 brain, and, during some stages of its existence, is closely connected 



1) Zur Entwickelungsgeschichte des Ceratodus Forsten. Anat. 

 Anz., Bd. 21, No. 21 und 22, 1902, 28. Aug. 



2) loc. cit. 



