76 [OIRNAI. OF COMPARATIVK NkIROLOGY. 



between the clusters of Deiter's corpuscles; in the second 

 they separate into uniform parallel bundles; in the third 

 they radiate in all directions. 



Tc€nia Thalami. — Near the meson and dorsad to the 

 peduncular tract, these fibres enter the prosencephalon. Im- 

 mediately they turn dorsad, and, if I have traced them cor- 

 rectly, after passing dorsad for a short distance they turn 

 laterad. After traversing about half the width of the hemis- 

 phere the tract again turns dorsad. Always keeping near the 

 caudad extremity of the hemisphere, it continues dorsad and 

 disappears near the dorsal surface of the brain. 



Tract us Bum/iii (Plate VI, Figs. 7-9). — This tract orig- 

 inates in either the frontal or fronto-median lobe and passes 

 caudo-ventrad through the intra-ventricular lobe. After 

 passing beneath the anterior commissure it turns and passes 

 ventro-latero-caudad to the crura cerebri. Penetrating the 

 dorsal part of the crura it passes to the outer fibre layer 

 of the tectum opticum. This tract does not decussate. It 

 connects the mesal wall of the ventricle of one side of 

 the brain to the optic lobe of the same side. To the best of 

 my knowledge, A. Bumm(') is the only one who heretofore 

 has accurately described this tract. He called it, " Mark- 

 bundle der strahligen Scheidewand."' This name being too 

 formidable for English readers, I have ventured to name this 

 tract, after its discoverer, Tractns Bummi. 



RECAPITULATION. 



1. In addition to and distinct from the anterior commis- 

 sure, there is a corpus callosum. 



2. There is a fibre tract connecting the mesal division of 

 the mantle with the optic lobe of the same side. 



3. In diflferent avian prosencephala corresponding areas 

 are supplied with similar cells. 



4. In the mantle and axial region of the procephalon 

 there are two types of cells, fusiform and pyramidal. 



I Op. cit., p. 451. 



