OLFACTORY CENTERS IN TELEOSTS Pg Ne 
petal fibers tothe nucleus medianus; nucleus supracommissuralis, 
nucleus preopticus and the primordium hippocampi, probably 
also to the nucleus commissuralis lateralis (¢r. olf. med.) ; in addi- 
tion to further fibers for the lobus pyriformis. The only portions 
of the basal lobes which do not receive secondary olfactory fibers 
are the nucleus entopeduncularis and, possibly, a small area in the 
center of the palaeostriatum. It can not be said with certainty, 
however, that this latter area receives no olfactory fibers of the 
second order; simply that such were not demonstrated. 
b. The anterior commissure 
The olfactory areas of the two basal lobes are connected by 
four sets of commissural fibers, crossing in five bundles. In the 
most rostral part of the anterior commissure are found numbers of 
fine fibers, partly medullated and partly unmedullated, bending 
sharply dorsad. The unmedullated fibers connect the mesal 
portions of the two primordia hippocampi, while the medullated 
join similar parts of the partes supracommissurales of the corpus 
precommissurale (Sheldon, ’09 a, fig. 6). A short distance 
caudad, accompanied by unmedullated fibers, is.a small commis- 
sure of medullated fibers connecting the lateral portions of the 
partes supracommissurales and nuclei dorsales or primordia 
hippocampi (figs. 35, 36). This latter bundle, as it presents 
points. of resemblance with the commissura pallii anterior of 
reptiles, and the rostral portion of the commissura pallii or com- 
missura dorsalis of Amphibia, is termed on the plates, commis- 
sura dorsalis. Morphologically, however, the fibers mentioned 
thus far are divisible into a commissura hippocampi, pars anterior, 
and a commissura corporium precommissuralium, each bundle 
consisting partly of each kind of fibers (fig. 138). 
At the caudal part of the anterior commissure a few unmedul- 
lated fibers pass across to connect the rostral ends of the nuclei 
preoptici of the two lobes. This is termed the commissura nu- 
cleorum preopticorum (fig. 138). 
The commissura dorsalis is closely associated with the decussa- 
tion of the tractus hypothalamo-olfactorius medialis and also with 
