The brain of Acipenser. 115 
feriores, is a nucleus which is crescent-shaped in frontal section 
(Phot. 22). It is the nucleus Gli of GORONOWITSCH and is the only 
well defined nucleus in the central grey of the thalamus. I shall 
show below that this nucleus is the place of ending of a bundle of 
fibres coming from the epithelial cells of the saccus. I have traced 
some of the neurites of these cells directly caudad into the base of 
the mid brain. 
The cells of the greater part of the grey matter have the most 
various shapes. They have either several dendrites which spread 
laterad or two which are disposed longitudinally parallel with the 
inner surface. The neurites may arise from any part of the cell 
body or from any part of the dendrites, sometimes being formed as 
a continuation of a long dendrite, as in the case of certain cells of 
the tectum described above (page 105). Fibres of the tractus strio- 
thalamicus medius seem to break up here although it is difficult to 
determine this point. The neurites of the cells usually run laterad, 
sometimes cephalo- or caudo-laterad, and seem to join the tractus 
tecto-lobaris, in which they must run to the tectum. If this be the 
course of these fibres, they constitute a tractus thalamo-tectalis and 
the cells from which they arise are equivalent to the nucleus rotundus 
of authors. 
3. Nucleus ruber tegmenti. 
This nucleus covers almost the whole lateral face of the thalamus 
caudal to the optic tracts (Phots. 20 and 22). It is bounded 
mesially by heavy bundles of medullated fibres, chiefly the crossed 
tractus lobo-cerebellaris et bulbaris, and dorsally by the direct 
tractus lobo-cerebellaris et bulbaris (see below, page 134). A very 
large number of fibres of the latter tract pass through this nucleus. 
In some GOLGI preparations the cells of the nucleus appear densely 
packed among the fine fibres of this tract. In preparations in which 
these fibres are not impregnated the cells stand out clearly on a 
transparent yellow ground, there being no heavily medullated fibres 
present. 
The cells are stellate, cubical or pyramidal in form and measure 
11—18 by 13—32 u. The dendrites spread in all directions, although 
frequently fusiform cells are seen with one dendrite directed centrally 
and the other toward the ectal surface. The neurites arise usually 
from the cell bodies. In all my preparations in which the neurites 
can be found they run with the fibres of the direct tractus lobo- 
8* 
