STUDIES ON THE NERVOUS SYSTEM OF CRUSTACEA. 4.77 
make no definite statement. When the fibres are stained in 
two or three successive ganglia, as is generally the case, the 
appearance presented is that given in fig. 11. The fibres from 
different ganglia run very close together, and it is impossible 
to differentiate them individually. In a few cases, however, 
the fibre of only one ganglion has stained. The most interest- 
ing of these is represented in fig. 12, A. The abdomen was first 
examined at a somewhat early stage of the staining, when in 
the ganglion of Abd. II the Y-shaped bifurcation was coloured. 
The anterior arm of the Y was actually traced as far as the 
posterior end of Th. XI (last thoracic ganglion), but could not 
be followed further on account of the flexure. The posterior 
arm was traced through Abd. III and through Abd. IV, but the 
staining had ceased before Abd. V was reached. After the 
staining had proceeded for some time longer, the appearance 
represented by Abd. II was that shown in fig. 12, B, and the 
corresponding fibres in the other abdominal ganglia were com- 
mencing to stain. 
As these elements often stain when the ganglionic cord is 
cut across at the level of the cesophagus, and when there is no 
visible wound behind that point, it seems possible that they 
may run forwards as far as the brain, although this is at 
variance with the conclusions arrived at by Lenhossék and 
Retzius for similar fibres in other Invertebrates. 
I may here mention that similar cells to those just described 
I have found in large numbers on the wall of the cesophagus of 
Astacus. 
N. 
In Th. I and Th. II there are two nerve-endings in connec- 
tion with which no cell has ever stained in the cord, although 
the fibres stain with very great frequency. It is not unlikely 
that these are sensory nerves, whose cells lie outside the cord. 
That of Th. I, which enters at the posterior root, is figured in 
fig. 18, whilst that of Th. II is inserted in fig. 1 at N. The 
latter is the more striking of the two on account of the fact 
that it not only branches in Th. II, but also sends stout 
