52 yourual of Comparative Neurology and Psychology. 



No certain conclusions could be reached by my method as to 

 the shorter connections between the tuber cinereum and the lobi 

 inferiores and in the lobi inferiores themselves. Golgi prepara- 

 tions alone could show these connections which certainly do not 

 form distinct tracts. The most important connections, however, 

 those with other parts of the brain, were found and exhibit a 

 resemblance to those of the bony fishes. The homology of the 

 three frontal attachments has already been pointed out and does 

 not need to be repeated here: the tr. strio-thalamicus with its 

 median bundle constituent and the tr. pallii, with the three frontal 

 tracts of the teleosts, viz., the tr. strio-thalamicus and the tr. 

 olfacto-hypothalamicus lateralis et medialis. 



The conclusion of my comparative study of the histology of the 

 fore-brain and 'tween-brain of the bony fishes and selachians was 

 that in the lobi anteriores of the former there are regions which in 

 the selachians are situated in the pallium. This was proved 

 (i) by the ending of the secondary olfactory tracts in the fore-brain; 

 (2) the situation of the bilateral commissure of the secondary 

 olfactory centers; (3) by the hypothalamic attachments of these 

 centers. The fact that in the selachians the tr. pallii is strongly 

 medullated, while in the teleosts the tr. olfacto-lobaris lateralis 

 is unmedullated does not invalidate this homology. On the 

 contrary, the region connected with the tr. pallii in the sharks is 

 much more extensive than the corresponding region related with 

 the tr. olfacto-lobaris lateralis in the teleosts. This difference 

 was to be expected, as well as the difference we found between the 

 two fasciculi retroflexi of the sharks, one of which, attached to 

 the larger ganglion habenulae, is medullated, while the other, 

 attached to the smaller ganglion and less highly functional, is 

 unmedullated. Even this is not so surprising as the fact that 

 until now Haploidonotus (C. L. Herrick) and Gadus are the 

 only fishes in which this lateral tract has been found with absolute 

 certainty (certainty at least in Gadus), for I did not find the tract 

 in Lophius, nor in Thynnus, Salmo, nor Gobius capito, nor did 

 Goldstein find it in the fishes examined by him. In the other 

 fishes the function of the two olfacto-hypothalamic tracts of the 

 selachians and Gadus and Haploidonotus must be included in 

 the medial tract of that name, which I have found in all of the 

 fishes examined. 



Haller has already suggested the homology of part of the lobi 



