THE TELENCEPHALON IN CYCLOSTOMES 389 
Fig. 21 The ninth section of the same series. Note the difference between 
the cells in the primordium hippocampi and those in the subhabenular region. 
The tractus olfacto-habenularis occupies a position in the eminentia thalami 
which is quite typical for vertebrates generally. The great number of longitudi- 
nal fibers in the primordium hippocampi are only indicated by a few lines. 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 22, NO. 4 
