102 J. B. JOHNSTON, 
In Goz&r sections, however, there are readily noticeable two 
zones in which fibres are more numerous. One of these zones 
occupies the middle one-third of the thickness of the tectum and 
in places, especially near the mid-dorsal line, extends into the inter- 
nal one-third. The second zone occupies the outermost part of the 
tectum, seldom extending deeper than the external one-fifth. I shall 
refer to these zones as the middle and superficial fibre zones. 
The inner zone of cells includes glia and nerve cells, both of which 
have radial processes extending toward the ectal surface. In the 
thicker ‘‘molecular“’ zone the cells seem to be nearly all nerve cells. 
I shall proceed to describe the cells of both zones, grouping them 
into five types according to the form of the cell body, the character 
and position of the dendrites, and the probable destination of the 
neurite. In determining the function and classification of the cells, 
the disposition of the dendrites and neurites are by far the most 
important considerations. 
1. Cells of Tectum. (Fig. F.) 
Type A: cells with radially placed dendrites and short neurites 
(Phots. 50, 51). These cells have ovoid or fusiform bodies which 
are usually placed in the inner cellular zone and have central pro- 
cesses reaching the cavity. They may stand in the inner one-third 
of the molecular zone and have no connection with the central ca- 
vity. The cell bodies measure 6—32 by 12—40 w. They may, 
however, be divided into two groups according to the size of the 
cell body and the size and number of the dendrites. The smaller 
cells measure 6—12 by 12—18 u, have each a single thick dendrite 
which rises straight to the periphery, and breaks up in profuse 
branches in the outer one-sixth of the tectum. The larger cells 
measure 12—18 by 24—40 u, have each a large dendrite which 
immediately or soon divides into several large branches which diverge 
as they rise toward the periphery and break up in the outer part 
of the tectum as do those of the smaller cells. The dendrites of 
both large and small cells are coarse and rough, often showing 
characteristic spines which differ from those on the dendrites of the 
PURKINJE cells and resemble those on the dendrites of cells in the 
lobi inferiores and the epistriatum, in that they bear small knobs 
at their ends. The neurite, in the case of all the cells of this type, 
arises from the dendrite at some point, usually a short distance 
beyond the first division of the dendrite. It thus happens that the 
