OLFACTORY CENTERS IN TELEOSTS on kal 
the entire extent of the crura; for a short distance at the rostral 
end of the basal lobes the two are so closely joined, however, that 
it is difficult to identify them (figs. 24, 34). As they come into 
proximity to the anterior commissure they again separate, the 
tractus olfactorius medialis, pars lateralis holding a_ position 
dorsal to its smaller companion tract (fig. 34). From this point — 
caudad it extends slightly laterad until the anterior commissure 
is reached, when it largely decussates at about the middle of the 
commissure, to end in the lobus pyriformis of the opposite side 
(figs. 35,.36, 55, 137). This agrees with the more lateral por- 
tion of the ‘mediale Riechstrahlung’ of Goldstein but differs 
from the conditions observed by Kappers, excepting for a few 
fibers in the brain of Salmo. A small number of fibers, however, 
as shown by Golgi preparations, leave the tract before its decussa- 
tion to end in the nucleus preopticus (fig. 137) and the pri- 
mordium hippocampi. The tractus olfactorius medialis, pars 
medialis originates from mitral cells of the medial surface of the 
bulb, and extending to the basal lobes, decussates ventral to and 
slightly rostral to, the tractus olfactorius medialis, pars lateralis 
(figs. 34, 35, 186). This forms the commissura olfactoria inter- 
bulbaris of Goldstein, the commissural fibers connecting the 
two olfactory bulbs, which have been described by many writers. 
In Weigert preparations it appears as if these fibers actually form 
a commissure, but when the crossing is examined in Golgi and 
Ramon y Cajal material, it is found that a large part of the fibers 
decussate in the commissure and then end almost immediately, 
while a few terminate at the commissure, without decussation. 
Many fibers terminate, also, in the pars anterior of the nucleus 
medianus, the pars supracommissuralis of the corpus precommis- 
surale and possibly in the primordium hippocampi of the same 
side. It can not be stated with certainty that no fibers pass 
around to the opposite bulb; commissural fibers have, therefore, 
been indicated on the diagram (fig. 124). Kappers, Edinger, 
‘Bellonci and others have noted fibers belonging to the medial 
olfactory tract, and ending: in the hypothalamus. Such an 
appearance is likewise common in Weigert preparations, as the 
fibers of the tractus olfactorius medialis, pars lateralis appear 
