Houser, Zhe Neurones of a Selachian. 153 
of the largest variety of neurone of the pallial eminence will 
be seen by referring to Fig. 39. This type assumes a variety 
of guises, but it is characterized by its larger size and by the 
fact that its axone enters the tractus pallii. The cell-body of 
such a neurone ranges from broadly oval to distinctly polygonal 
in form. The dendrites are long and widely spreading proc- 
esses, arising through thick basal masses at three or four almost 
equidistant points. A dendrite branches once or twice, dichot- 
omously asa rule, and the terminal lengths become quite 
slender. Its surface is slightly roughened by minute gemmules. 
These are far less conspicuous, however, than the gemmules 
observed in the neurones of the striatum. 
The internal structure of one of these neurones is shown 
in Fig. 68, p. 4. x. The organization is markedly motor in type. 
There is an abundance of cytoplasm investing the nucleus on all 
‘sides. The nucleus is a sharply defined, central body, with a 
single nucleolus, and chromatin which is disposed in a condition 
strongly suggestive of a reticulum, although not actually ap- 
pearing so. The tigroid-bodies are quite large in the region of 
the nucleus, the largest, in fact, of any tigroids found in the 
forebrain. More slender tigroids extend into the dendrites for 
some distance. In the cell figured, the axone exhibits a small 
axone-hillock of oval form. 
The axone arises from the cell-body, (Fig. 68, p. ¢. 2.), or 
from the thickened base of a large dendrite, (Fig. 39). It pur- 
sues a staight course, although one with many local sinuosities. 
The several axones of this class come to lie in the superficial 
zone, and they are gathered into a longitudinal bundle which 
lies as a broad cap on the neurone-aggregate of the pallial 
eminence (Fig. 31, %. g.). This is the beginning of the tractus 
pallii. The pallial tract runs backward to the great posterior 
curve of the forebrain, where it dips ventrally to the base and 
enters the interbrain. Here it decussates and passes onward 
toward the oblongata. The tractus pallii is the Mantelbiindel of 
EDINGER (’88). 
b. Associative and Commissiral Neurones.—A second type 
of neurone found in the pallial eminence is distinguished from 
