The brain of Acipenser. eal 
front of the epiphysis the habenular commissure is superficial in 
position. Very soon it comes to be covered dorsally by an extension 
of the third ventricle closed over by the choroid roof of the 'tween ~ 
brain. This is the most caudal part of the paraphysis. At the same 
time there appears on the dorsal (still ental) surface of the fibre 
layer of the ganglion habenulae a mass of cells. This cell layer is 
large on the rigth and almost imperceptible on the left. Farther 
forward it joins the ventral mass of cells in a horseshoe-shaped cell 
layer, the concavity of which is directed laterad and is filled by the 
fibre layer. On the right side the bundle of MEYNERT as it enters 
the ganglion becomes divided into a number of small, compact and 
distinct bundles which are distributed around the concave border of 
the cell layer and appear cut across in frontal sections. Each of 
these bundles is separated from its neighbor by transverse bundles 
connecting the cell layer with the fibre layer. This peculiar and 
characteristic appearance on the right side is wholly lacking on the 
left, where no regular arrangement of the cells and fibres is to be 
made out, further than an imperfect separation of the two layers. 
Toward the cephalic end of the ganglia large bundles of fibres, very 
distinct on the right side, go from the fibre layer downward and 
forward toward the fore brain. The larger size of the right ganglion 
is due to a greater mass of both cells and fibres. 
In GOLGI preparations the minute structure of the ganglia is 
found to be relatively simple. The cells are very well shown in 
Phot. 68. They are pyramidal or pear-shaped and measure 16—18 
by 16—28 u. One thick dendrite arises from the apex and some- 
times one or more smaller dendrites from some other part of the 
cell. The cell body stands near the cavity and the large dendrite 
is directed ectally or ventrally. From some part of this dendrite 
arises the neurite which passes toward the caudo-ventral angle of 
the ganglion and joins with its fellows to form the bundle of Mry- 
NERT. On the left side the fibres, which are medium-sized with a 
few finer ones among them, converge from all parts of the ganglion 
to a common bundle. On the right side medium-sized and fine 
fibres are present in about equal numbers. Near the ganglion the 
two sets of fibres are gathered into two distinct bundles, the mesial 
one of which contains the finer fibres (Phot. 67). As the whole 
bundle enters the ganglion the fine fibres course around the con- 
cavity of the horseshoe in the position occupied by small fascicles 
mentioned in the last paragraph. Although the cell bodies in the 
