264 THE BRAIN OF THE TIGER SALAMANDER 



of sagittal Golgi sections (no. 2215), in which the tr. habenulo- 

 interpeduncularis is impregnated, a few thick axons are seen to arise 

 in the gray of the dorsal thalamus and join the f . retroflexus, which 

 they accompany almost to the ventral surface. Here some of them 

 end by wide arborization in the area ventrolateralis pedunculi. This 

 area of neuropil, accordingly, receives fibers by way of the f . retro- 

 flexus from both the habenula and the dorsal thalamus. 



The connections just described are a simplified version of the com- 

 plicated structure of the f. retroflexus of Ceratodus described by 

 Holmgren and van der Horst ('25, p. 105). The fact that the atypical 

 arrangements occur on only one side in Amblystoma probably is ex- 

 plained by the asymmetry of the habenular system in Ceratodus and 

 other primitive species. 



