Heukick, ^forf^Jiolooy of Nervous System. 17 



occipito-basal lobe from the diencephalon, entering dorsad 

 to the peduncles. If correctly followed, these fibres have 

 their origin in dense cell-masses near the middle of the 

 thalamus at about the level of the dorsal part of the anterior 

 commissure. 



A distinct bundle from the anterior commissure may be 

 traced to this lobe, though its exact destination is not 

 known. But, inasmuch as the tract can be followed to 

 the median part of the lobe and a well-defined nidulus(') 

 lies in their course produced caudad and laterad, it is 

 natural to conclude that the two are related. 



This occipito-basal nidftliis is not a single cell cluster, 

 though it contains a central aggregate which is sharply 

 defined. A short distance dorsad to the ventro-basal pro- 

 tuberance of this lobe a few rather large fusiform cells with 

 large pale nuclei appear in clusters along the caudad border 

 of the lobe. These become more numerous in regions far- 

 ther dorsad and accumulate in small clusters, which fuse 

 at a level somewhat dorsad to the anterior commissure to 

 form the axial nidulus of the lobe above referred to. Such 

 nests or aggregates seem to be a constant feature in all rep- 

 tilia. We have observed them in the Chelonia, Ophidia, 

 and Sauria (see notes upon the brain of the alligator, Plate 

 VII, Figs. 7 and 8). Mr. Turner finds similar proliferating, 

 areas in the corresponding region in birds. 



In the black-snake a distinct fibre-tract from the caudad 

 strands of the anterior commissure passes to the caudad 

 or ventricular surface of this lobe and passes to its laterad 

 portion. The cells of the lobe in this case are beautiful 

 illustrations of flask cells with apical processes chiefly 

 median. 



In the frog the occipito-basal lobe is well developed, but 

 is very simply constructed, consisting of numerous more or 

 less concentrically arranged flask cells with fibres passing 



I A substitute for the word " nucleus " as applied to central ceU clustery, 



