No. 5.] HABENULAR TRACTS OF ACIPENSER. 235 



ever, in the ganglia habenulae the fibers in question cross to 

 the opposite side through the commissura habenularis and 

 seem to end by free branching among the dendrites of the 

 cells which give rise to the bundles of Meynert. This renders 

 it probable that these fibers constitute the tractus olfacto- 

 habenularis (Fig. 3, Tr. olf.-hab.; Fig. 4, E). 



I will here insert a note on the course of the bundles of 

 Meynert as throwing light on the function of the olfactory 

 nuclei as well as on that of the ganglia habenulae. For these 

 conspicuous bundles traversing the internal faces of the walls 

 of the 'tween-brain I have not adopted the name proposed by 

 Edinger, tractus habenulo-peduncularis, for the reason that 

 in Acipenser their fibers do not end in the corpus interpedun- 

 culare as described by Mayser ('82), Van Gehuchten ('94), Edin- 

 ger ('96b), and S. Ramon y Cajal ('96b) for other forms. In the 

 corpus interpedunculare a majority of the fibers of the bundles 

 of Meynert cross to the opposite side, and both the crossed 

 and uncrossed fibers pass on back toward the medulla. I have 

 not traced them to their endings. I give a figure (Fig. 5) of 

 the course of the fibers through the corpus interpedunculare. 



(4) The cortex. Among the fibers from the lateral nucleus 

 postolfactorius and striatum on the lateral and ventral surfaces 

 of the fore-brain occur cells measuring 12 to 18 by 16 to 40 /* 

 with two or more dendrites usually disposed parallel with the 

 external surface (Fig. 3). In the anterior commissure are 

 found a small number of thick fibers with very definite, round 

 varicosities at regular intervals (Fig. 3, assoc. f.}. In a few 

 cases I have found the axis cylinders arising from the super- 

 ficial cells just mentioned directed toward the anterior commis- 

 sure and having the characters of these thick fibers. Tracing 

 the fibers, they are found to end in the epistriatum in the 

 manner described above. Some of the cells of this region 

 have very slender, smooth axis cylinders directed toward the 

 anterior commissure. I have been unable to trace them to 

 their destination. The fibers which end among these cells are 

 collaterals from the axis cylinders of striatum cells, occasional 

 short axis cylinders from the epistriatum, and probably fibers 

 from the tractus olfactorius. 



