120 



Id the Selachians 1 do not find the mass of cells indicated by 

 PiNKUs in Protopterus, as the peripheral termination of the nerve, but 

 on the other hand, I have traced the fibers of the new nerve between 

 the folds of the nasal epithelium. 



Through the courtesy of Dr. Bashford Dean of Columbia Uni- 

 versity, I have had the opportunity to examine a specimen of the 

 brain of Protopterus. I readily found the nerve as located by Pinkus, 

 but, on account of the condition of the single specimen I had for 

 examination, only a few details could be made out. I noticed, however, 

 two short roots connecting it with the brain surface where the re- 

 construction of PiNKUs shows a single strand. The nerve was broken 

 anteriorly and could not be traced in the region of the olfactory cups. 



Allis, in 1897^) described a somewhat similar bundle in both 

 young and adult stages of Amia which he believes to correspond to 

 the nerve described by Pinkus. He found no ganglion and was not 

 able to trace the nerve to its peripheral distribution. I have examined 

 this bundle in the brain of the adult Amia. It does not have the 

 conspicuous separateness which characterizes it in the selachian brain. 

 In Amia it is closely united with the tractus and is not nearly so 

 distinct, even where it runs over the ventral surface of the brain. 



At the time of writing my former paper for the Anatomischer 

 Anzeiger, I called attention to the work of Pinkus, but, expressed 

 doubt as to the honjology of the nerve described by him with that" 

 in the Selachians. It has a dorsal connection with the brain in the 

 only two forms — Squalus and Raja — in which I had observed it, 

 while its connection in Protopterus is ventral. 



It appears to me now, öfter observing the nerve more widely 

 in Selachians, in which it has both a ventral and dorsal position, that 

 it corresponds with the nerve described by Pinkus in Protopterus and 

 by Allis in Amia. 



Johnson '-^j has suggested that the nerve in Selachians belongs to 

 the first brain neuromere, and that of Pinkus to the second neuromere 

 but, its variable position, and gradations leading from a i)urely dorsal 

 position to a purely ventral one, leads me to adopt the idea of the homo- 

 logy of nerves in Selachians and the Dipnoi. The point of its surface 

 connection with the brain, is not so significant as its central terminations. 

 Although we do not know its central terminations in Protopterus there 

 are reseuiblauces of a broad and general character between the nerves 



1) Journ. Morph., Vol. 12, 1897. 



2) Ergebnisse d. Anat. und Entwickel., Bd. 11, 1901, p. 1010. 



