130 JoURNAL OF CoMPARATIVE NEUROLOGY. 
lying very close to the median plane send their axones to the 
opposite side; but the remaining members of the group, com- 
prising nearly all of the cells, have their axones extending away 
from the mid-line. The axones from the several cells of the 
same side, together with the crossed axones, run laterally for 
a greater or less distance, turn anteriorly, and become associ- 
ated into bundles which constitute a fairly well-marked tract 
(Figs. 20 and §5, 7. ~. ¢.). This tract extends forward to the 
anterior limit of the midbrain, where it unites with its fellow 
from the opposite side, and the united group of fibres emerges 
from the midbrain roof to penetrate the aqueduct of SyLvius 
as the fibre of ReissNER. The ultimate destination will be 
traced in a subsequent paragraph. 
Those cells of the roof-nucleus lying in the posterior region 
have a different termination for their axones from the one just 
described. In this instance, the axones pass posteriorly, instead 
of anteriorly, and they take a course into cerebellum. The 
significance of this fact has been considered in Section V, Sub- 
section 5. 
The cell-nucleus is a large, evenly rounded body, almost 
invariably eccentric in its position, sometimes, even, lying in 
what appears to be a special protrusion of the general cell-mass. 
The chromatin is distributed in the form of a reticulum of rather 
fine mesh which holds coarser granules at intervals. The nucle- 
olus is evenly rounded and of conspicuous size. Many of the 
cells have two or even more nucleoli. 
The cytoplasm, stained with methylen-blue, exhibits a 
minutely punctate appearance even under the highest amplifica- 
tion, due, chiefly, to the minute size and diffuse distribution of 
the tigroid substance. The tigroids are quite densely packed 
in the peripheral regions of the cell. In the field of the nucleus, 
the prevailing form of granule is rounded ; farther away, the 
shape is a more elongated one, the long axis being tangential to — 
the margin of the cell. Fig. 56 shows the details of cell-organ- 
ization, NIssL staining. 
When these cells are stained with iron haematoxylin, they 
exhibit what appears to be the equivalent of the perinuclear 
