Nuclei Tuheris Laterales and the Ganglion Opticum Basale. 11 



line. In Fig. 13 the cell column along the medic-caudal border of the 

 tract, as well as the scattered cells dorsal to the tract, appears, and 

 from here throughout the entire series these three columns are present. 

 Of course all columns are in cross section. In Fig. 18 the cell mass is 

 seen to extend across the median line, a condition which occurs also in 

 the three other series of man. Series D (Figs. 11 to 18) shows clearly 

 that the basal optic ganglion consists of two well developed parallel 

 columns of cells connected by an intermediate parallel column consisting 

 of only a few cells. As will be shown later the exact extent of the 

 basal optic ganglion in all the mammals studied is readily determined 

 by the distinctive histological character of its cells, and accordingly the 

 three parallel cell columns have been considered as merely subdivisions 

 of one nucleus, not because this seems convenient, but because the 

 identical character of their cells makes such a conclusion unavoidable. 



MAC.A.CUS RHESUS. 



In maeaeus rhesus the basal optic ganglion is shown first in Fig. 22, 

 although it extends slightly further caudally. In tliis figure the gang- 

 lion is situated just oral to the line of apposition between the tuber 

 cinereum and the optic tract. In the sections between Figs. 23 and 23, 

 as we pass orally, the cells become reduced in number and lie dorsal to 

 the tract, and as the oro-lateral border of the tract is reached increase 

 in number. In Fig. 23 appears the cell column which lies in the ante- 

 rior perforated substance along the oro-lateral border of the tract. The 

 further development of the ganglion (Figs. 21: and 25) needs no 

 description. In Fig. 22 the medial pole of the ganglion is seen to 

 approach the median line, and between Figs. 22 and 23, just caudal to 

 the optic chiasm, a very few widely scattered cells unite the ganglia of 

 opposite sides. As in man the basal optic ganglion in macacus is 

 seen to consist of tlie same three parallel columns of cells, of which the 

 oro-lateral column (situated in the anterior perforated substance) con- 

 stitutes the greater part of the ganglion. 



LEMDR RUFUS. 



The basal optic ganglion of the lemur does not differ essentially 

 from that of man and maoacus, except that whereas in the two latter 

 animals it consisted of two parallel cell columns loosely connected by 

 a third, in the lemur this connecting mass of scattered cells (dorsal to 



