12 'Journal of Cotnparative Neurology and Psychology. 



Bellonci for Macropodus and Anguilla. Regarding the rela- 

 tions of the last-mentioned part of the commissure, which he calls 

 the "chiasma olfattoria," this author says that it is situated 

 "subito sopra ed indietro la commissura trasversa olfattoria"; 

 by which name he denotes the foremost part which I described 

 above. 



It should be added here that in some fishes the structure of the 

 commissure differs from that of Gadus, Lophius and Thynnus. 

 Thus it has been stated by Goldstein that fibers of the lateral 

 olfactory tract form a part of it, as I can confirm for Salmo salar, 

 as stated above. These, however, are not all the component parts 

 of this commissure. In Gadus and Lophius there are between 

 and under these two parts unmedullated fibers originating from 

 the area where the medial olfactory fibers end and the medial 

 hypothalamus bundle begins, and in Salmo there are a great many 

 fibers that connect the back parts of the medial secondary olfac- 

 tory lobe, as was first described by C. L. Herrick under the name 

 of hippocampal commissure and as Dr. Goldstein confirms for 

 many fresh water fishes. I have seen the same in Salmo. 



Finally I have to mention some fibers of which it is difficult to 

 say whether they originate from the medial olfactory area (epi- 

 striatum) or from the striatum. These fibers also form a bilateral 

 connection and do not enter one of the longitudinal tracts. The 

 difficulty in establishing the real origin of the last-mentioned 

 fibers does not lie in the fibers themselves, which are very distinct, 

 but in the determination of the boundaries of the different regions 

 of the fore-brain, which must be distinguished mainly by their 

 connections, since in most of the fishes examined the shape 

 of the cells, though varying greatly, is scarcely typical for the 

 different parts, for different types of cells occur in almost every 

 region. 



We have now defined two important parts of the lobianteriores, 

 the area olfactoria posterior lateralis and the area olfactoria rnedi- 

 alis, or eptstriatum, terminal centers of secondary olfactory 

 tracts and centers of origin for the caudal attachments. Another 

 not less important part of the anterior lobe, however, is formed by 

 the striatum mentioned above. This cell mass is bounded latero- 

 ventrally by the area olfactoria posterior lateralis and latero- 

 caudo-dorsally by the area olfactoria medialis. From this rela- 

 tion it appears that the striatum itself is for the most part free 



