126 JOURNAL OF COMPARATIVE NEUROLOGY. 
gential to the surface of the brain, as though squeezed into 
crevices between the mass of nerve-fibres. The internal organ- 
ization of the cell presents no features which would mark it as 
having any degree of importance physiologically (Fig. 52, s. z.). 
c. The Middle Neurones.—The neurones which lie in the 
middle layer of the tectum are characterized by their larger 
size and vastly greater numbers as compared with the outer 
region. In fact, the number is so great that in a section, the 
nerve-cells often appear superposed one over another, and 
the processes make a veritable tangle of interlacing branches 
(Fig. 21, m. 7.). 
The neurones of the level are to be distinguished from 
those of the deeper layer, on the other hand, both by their 
compactness and by their mode of branching, which is of the 
radiating type. The several processes of a nerve-cell spread 
out and branch freely in all directions, but they do not extend 
far away from their points of origin. A representative form 
is drawn in Fig. 22. There are always several dendrites, and 
these may arise either from the outer end or from the side of 
the polygonal cell-body. The branching begins quite near the 
origin, so that the size diminishes rapidly from the base out- 
ward. The dendrites of the outer extremity have their finest 
twigs penetrating the superficial layer of nerve-fibres. The 
dendrites arising from the sides of a cell interlace more largely 
with those of other neurones. The surface of a dendrite always 
bears an abundance of simple gemmules. 
The axone pursues an irregular course, often spreading 
over a considerable horizontal area, but the general trend is 
ever toward the centre of the brain. It gives off a great pro- 
fusion of collaterals as it proceeds, and the final termination is 
found at no great distance from the cell-body. There is here, 
then, an illustration of a cell of the Gorcr II type. The sev- — 
eral ramifying axones lie in the region occupied by the cells of 
the deeper layer. Pp 
The nucleus is a rounded, centrally located body, filling 
the larger part of the mass of the cell. The cytoplasm holds 
a few tigroid-bodies of small size, an evidence of a low order 
