192 'Journal of Comparative Neurology and Psychology. 



Until very recently, however, its presence in forms other than the 

 selachians, ganoids and dipnoans has not been demonstrated. At 

 the Baltimore meeting of the Association of American Anatomists, 

 in a joint paper, Brookover and I reported its existence in teleosts, 

 describing its ganglion, and peripheral and central connections. At 

 the same time Herrick showed that it is also present in both the 

 larval and adult frog. 



This paper takes up in detail the central course of the nerve in 

 the carp, Cyprinus carpio. It consists entirely of a tract of un- 

 raedullated fibers which was traced by means of the following 

 methods and material. 



1. Weigert method. 



(a) Four transverse series of the entire olfactory crura, bulbs 

 and nasal capsules of adult individuals about 50 cm. in length. 



(&) Two longitudinal series through the olfactory bulbs and cap- 

 sules of similar adults. 



(c) Two transverse series through the cerebral hemispheres of 

 adults. 



(d) One transverse series through the entire head of a young- 

 carp about 2 cm. in length. 



These were stained by a modification of the straight Weigert 

 method which left the unmeduUated fibers a reddish brown. This 

 method was particularly valuable, as the tract is, for most of its 

 extent, surrounded 1)V meduUated fibers from which it stands out 

 quite distinctly. 



2. Vom Rath method. 



One transverse and one longitudinal series through the olfactory 

 crura, bulbs and capsules of an adult about 30 cm. in length. This 

 method also gave good results, as the unmedvdlated fibers appear 

 lighter in color than the medullated. 



3. Cajal method. 



Two transverse series through the cerebral lu'mispheres of an 

 adult about 35 cm. long. In my preparations tlie nervus terminalis 

 is an orange yellow, while the uu^dullated fil)ers suiToniiding it are 

 nearly black. These series were of especial value in showing the 

 decussation of the nerve in the anterior commissure. 



4. Toluidin blue and thionin methods. 



