OLFACTORY CENTERS IN TELEOSTS 235 
surale by way of the comparatively few fibrae precommissurales - 
striatici to the palaeostriatum and thence through the tractus 
strio-thalamicus, or else from the corpus precommissurale by 
way of the descending fibers of the medial forebrain bundle. In 
neither of these cases do we find so definite and compact a path- 
way as that first outlined, wherefore we may conclude that the 
first is the more usual path for the direct olfacto-motor reflexes. 
Another possible motor connection is through the preoptico- 
habenularis fibers to the habenular region, and thence through the 
fasciculus retroflexus, as above indicated. This is probably a 
very unusual pathway as the connections just mentioned are 
very diffuse and are undoubtedly simply the vestiges of a once 
powerful pathway, now of less functional importance (ef. Acipen- 
ser). The functions of these latter pathways will be considered 
lovers 
It is quite probable that there exist also somatic fibers connect- 
ing the epithalamic with the visual centers, although such were not 
demonstrated (Herrick, ’10b, pp. 468-469). The relation between 
the ventral hypothalamic region and the visceral (gustatory) 
pathways in teleostean fishes will be brought out later (see also 
the discussion in the above mentioned paper of Herrick). 
Ascending pathways 
There is no evidence for the existence of centrifugal fibers in 
the olfactory nerve bundles. Ascending fibers from the dien- 
cephalon include fibers from the lateral and ventral portions of the 
inferior lobes to the nucleus pyriformis (tractus hypothalamo- 
olfactorius lateralis); fibers from the ventro-lateral part of the 
inferior lobes, the nucleus prerotundus and nucleus anterior 
tuberis especially, and possibly the nucleus rotundus to the palaeo- 
striatum and nucleus olfactorius lateralis by way of the tractus 
thalamo-striaticus; and the fibers from the nucleus posterior 
tuberis to the corpus precommissurale. From the corpus pre- 
commissurale, nucleus medianus, fibers pass to the nucleus olfac- 
torius anterior in the tractus olfactorius ascendens (figs. 136, 137). 
