THE TELENCEPHALON IN CYCLOSTOMES 359 
The rostral bundle is composed of fibers fromthe first bundle 
described above and its fibers seem to end in the fiber-mesh of the 
right: nucleus (figs. 18, 19). The corresponding bundle of the 
right side meets with the left and seems to end with it in the right 
nucleus. 
The strands of the more caudal division of the commissure are 
made up of fibers of the remaining three bundles intermingled. 
Many of these fibers end in the fiber mesh of the right nucleus 
but many others pass through the nucleus without ending. This 
is especially evident in such horizontal sections as those drawn in 
figures 17 to 20. At least a part of these fibers clearly appear to 
be those which arise in the primordium hippocampi. If so, it is 
probable that these fibers end in the corresponding body on the 
other side and are homologous with the posterior pallial commis- 
sure which is prominent in selachins, ganoids, teleosts and amphi- 
bians. 
The fibers in the caudal division of the commissure which end 
in the right nucleus may include those parts of the tractus olfacto- 
habenularis which in other fishes arise in the lateral olfactory 
nucleus and in the nucleus praeopticus. These may also include 
fibers from the primordium hippocampi which would belong to 
the tractus cortico-habenularis. 
It seems reasonably certain from the study of these Golgi sec- 
tions that the stria medullaris contains the equivalent of the 
tractus olfacto-habenularis lateralis and posterior, and the com- 
missura palli posterior as described in the selachian brain. Nearly 
all of these fibers from the left side cross in the superior commis- 
sure. 
The writer has described (’02 a, pp. 38, 40) two afferent tracts 
ending in the primordium hippocampi; one ascending from the 
hypothalamus and one coming from the formatio bulbaris. The 
former has since been called tractus pallii in all fishes and is re- 
garded as the ascending gustatory tract entering the telencephalon 
for: the sake of correlation of gustatory with olfactory impulses. 
This tract decussates in the post-optic commissure and ascends 
over the internal face of the tractus opticus to enter the primor- 
- dium hippocampi from below and behind. 
