10 Journal of Comparative Neurology and Psychology. 



From the medio-caudal secondary olfactory center a median 

 tract of fibers arises, chiefly medullated, and goes backward along 

 the median fissure of the thalamus to end without decussation 

 (Gadus, Lophius, Salmo and Thynnus) in the hypothalamus 

 directly in front of the nucleus rotundus. Some of its fibers may 

 go into this nucleus, as Bellonci describes, which I could not 

 make out, since no Golgi preparations have been made. At 

 first I got the impression that this tract contains also a great many 

 secondary olfactory fibers and thus constitutes a direct connection 

 between the lobus olfactorius anterior and the lobi inferiores, an 

 opinion, however, which I no longer hold so firmly since my 

 investigations have been extended to a larger number of teleosts. 

 But still it may be possible that this tract, which according to 

 Johnston, is present in Petromyzon (tr. lobo-epistriaticus, 

 Johnston), in the teleosts contains some direct connections with 

 the anterior olfactory lobe, as Bellonci and after him Edinger 

 described. This tract for which I choose the name tr. olfacto- 

 lobaris rnedialis, or tr. olfacto-hypothalamicus niedialis, has been 

 well known for many years having first been described by Bel- 

 lonci in Anguilla as a direct connection between the nuclei 

 rotundi and the olfactorv bulbs. 



In Edinger's work of 1887 he stated that in Corvina the only 

 medullated tract of the commissura anterior extends in the direc- 

 tion of the 'tween-brain, and in his " Vorlesungen" he says, "Es 

 ist wahrscheinlich dass bei den Fischen Fasern von der Olfacto- 

 rius-schenkel der Commissura anterior riickwarts in den Hypo- 

 thalamus Ziehen." And Osborn, C. L. Herrick (fornix) 

 Haller and Catois all treat of this connection; however, there is 

 no certainty about its secondary or tertiary character. On 

 further examination of more material I get the same impression as 

 Goldstein, that this tract begins chiefly if not wholly without 

 decussation in the area olfactoria medialis, or epistriatum, and 

 that the decussating fibers of the region where it begins do not 

 belong to this tract but to those secondary medial olfactory fibers 

 that end where the tractus olfacto-hvpothalamicus begins. 



There are two other tertiary olfactory tracts connecting the lateral 

 part of the area olfactoria posterior with the thalamencephalon. The 

 first of these is the tractus oljacto-loharis lateralis, or tractus olfacto- 

 hypothalamicus lateralis, a compact large tract of unmedullated 

 fibers that gather from the area olfactoria posterior lateralis and 



