j6 Jc^rHNAl, <)!• CoMl'AHATI\K NeI' H()I,()(i^ . 



addition to the prevailing fusiform cells with pale nuclei, 

 many small dark nuclei, probably representing cellular 

 elements like those of the granular layer of the cerebellum. 

 The commissure does not seem like a decussation, and, 

 although it may sustain some relation to the conarium, 

 reveals none. Its convexity is caudad and dorsad, and its 

 tracts pass latero-ventrad until they approximate to the 

 optic tracts. It is impossible to determine at present 

 whether they fuse with the optic tract or cross into the 

 ventral part of the occipito-basal lobe. This tract comes 

 into close relation with the superior commissure tract, or 

 taenia thalami, but does not seem to fuse with it. We have 

 here the solution of the relations which puzzled Osborn and 

 myself in amphibia and the alligator. Instead of a division 

 of the superior commissure we have to recognize two origin- 

 ally distinct commissures. The commissura habenaria seems 

 to receive numerous fibres from the habena at a lower level. 



The supra-coiuniissura lies entirely cephalad to the ha- 

 bena at a level considerably ventrad to commissure of the 

 habena (which lies caudad to it), and passes by a slight 

 ventral curvature into the median part of the medio-caudad 

 projection of the cortex, and thence across to the caudo- 

 lateral portion. The superior commissure is relatively 

 stronger than its neighbor, and it would appear that the two 

 are especially distinct in animals like the lizard, where the 

 epiphysis is highly developed. 



If the superior projecting portion of the habena sur- 

 rounding the base of the stalk of the epiphysis be con- 

 sidered the habena proper, the deeper and more ventro- 

 caudad portion may be distinguished as the nidulus of 

 Meynert's bundle or nidulus Meynerti. The fibres of Meyn- 

 ert can be traced to the portion mentioned (which in the 

 black snake forms a distinct nidulus). The cells are rather 

 larger than those of the habena, and less compactly clus- 

 tered about the walls of the fourth ventricle extending 

 .some distrance ventrad. 



