Kappers, Teleostean and Selachian Brain. 19 



Passing now to the basal region of the fore-brain, two groups of 

 cells and their attachments remain to be described. 



6. One group of cells, the striatum, lies behind and under the 

 epistriatum. From this group the fibers of the tr. strio-thalami- 

 cus arise (Fig. xxii), at first a large mass of fibers with many cells 

 between and becoming more compact behind and medially and 

 then uniting with a part of the fasc. medianus in a single extensive 

 bundle. Where they unite (Figs, xxiii and xxiv) fibers of one side 

 pass to the other (commissura anterior), which, however, I do not 

 regard as a decussation of the fibers of the tr. strio-thalamicus. 

 The latter ends wholly uncrossed in the hypothalamus, as will be 

 described in the second chapter. 



7. Finally, there is a group of cells which is really the only one 

 very accurately known. It lies in the medio-basal part of the 

 distal fore-brain. It is the nucleus post-olfactorius, or nucleus 

 tcenice, which HousER has so accurately described. From it 

 there originates a bundle of medullated fibers (Fig. xxii), which 

 runs over the basal tract (Figs, xxiii, xxiv, xxv) and afterward 

 terminates in the most anterior nuclei of the ganglia habenulae. 

 I prefer to retain the name, nucleus taeniae, given by Edinger, 

 who has pointed out that this nucleus has a constant position in all 

 vertebrates; moreover the giving of new names can only cause 

 confusion. 



BoTAZZi does not mention this tractus olfacto-hahenularis, but 

 it is obvious that he describes this bundle as a root of the tr. strio- 

 thalamicus. I think that he likewise described the tr. olfacto- 

 epistriaticus homolateralis as a part of the basal bundle.^ 

 ■ Now, a few words more about the commissura anterior, whose 

 constituent parts are far less easily examined than in the teleosts, 

 and a part of which, called by Herrick the hippocampal com- 

 missure, I think, is represented in the decussatio inter-hemi- 

 spherica of the selachians. The commissura anterior itself is, 

 as I have already stated, for this reason not so strongly developed 

 in the selachians. It is possible, but not probable, that it contains 

 a part of the ventral olfactory fibers, though certainly this part is 

 very small, especially as compared with the strong development of 



^As the insertion of the lobi olfactorii is so much more basal in the selachians which Botazzi figures 

 than in Galeus canis, it can be easily understood that because of the basal situation of the basal bundle 

 in BoTAZzi's specimens he failed to recognize it and described it as a part of the tr. strio-thalamicus. 



