STUDIES ON THE NERVOUS SYSTEM OF CRUSTACEA. 47 
the element just described. It differs chiefly in the position 
of the cell, which lies in the posterior lateral portion of the 
ganglion. The fibre curves first upwards and forwards, and 
then downwards, when it divides into two branches similar to 
those of element a. 
The element J (4), which has already been described as 
occurring in the last ganglion of the thorax (fig. 1, Th. x1) is 
found also in the ganglion of the abdomen (Abd. 1-v), and is 
shown in figs. 2 and 3. The cell lies near the middle of the 
posterior end of the ganglion. The fibre runs at first forwards 
and outwards, and then turns inwards and backwards, giving 
off a small branch to the neuropile at the angle. Subsequently 
it divides into two branches, one of which passes out at the 
posterior root, whilst the other runs over to the opposite side 
of the ganglion, where it breaks up in the neuropile. 
The element D (figs. 2 and 3) arises from a comparatively 
small cell, which lies in the anterior half of the ganglion near 
the middle line. The fibre runs backwards and slightly out- 
wards, decussates with its fellow of the opposite side forming 
the characteristic figure represented in fig. 2, gives off a small 
arborescent branch to the neuropile, and then runs backwards 
to the posterior root of the ganglion through which it passes. 
ELEMENTS NOT CONFINED TO ONE GaNnGLion.—Two pairs of 
elements have taken up the stain in each of the abdominal 
ganglia, whose fibres pass out through one of the roots of the 
ganglion immediately anterior to that in which the cell lies. 
The element e (figs. 2 and 3) has the cell situated near the 
middle line at the anterior end of the ganglion. From the 
cell, which is small, the fibre runs outwards and backwards, 
and then, turning sharply inwards, runs as a transverse fibre 
close to its fellow of the opposite side. On reaching the other 
side it turns forwards, giving off an arborescent branch at the 
angle, runs into the next ganglion in front, and there passes 
out at the posterior root. When the elements upon opposite 
sides are stained it is generally impossible to distinguish the 
two transverse fibres, which lie so close together in this and 
