170 BULLETIN OF THE 
in size it is no longer possible for the ventral line with the entire nervous 
mass to be retained in its usual position. It is therefore forced up- 
ward into the body cavity, and fills a considerable portion of it (Fig. 9). 
In fact, near the end its diameter is half as large as that of the body 
at that point. 
Seen in cross section (Fig. 96) the nerve cord itself presents little 
here that is different from its general character throughout the body. 
It is the peripheral layer which demands particular attention. This 
is crescent-shaped, and composed of a dense matrix in which are embed- 
ded many nuclei. Along its periphery the matrix is finely striated per- 
pendicularly to the surface, and is separated from the underlying nerve 
cord by a narrow space filled with loose fibrous tissue (Fig. 97). The 
horns of the crescent are turned ventrad around the nerve cord, and are 
connected with the tissue lying below it. In these horns one sees a 
fine longitudinal striation ; occasionally more plainly marked fibres, 
coming from the cells above, may be traced into them. The matrix, 
which usually takes a faint stain, contains numerous oval nuclei (Plate 
V. Fig. 71) with a sharply defined nuclear membrane. The nucleus in 
general does not take up the stain, so that the one or two large nucleoli 
stand out in strong contrast to the rest. One can neither find any cell 
boundaries in the matrix, nor determine how much, if any, of the sur- 
rounding protoplasm belongs to each nucleus. In fact, the fibres which 
one finds often appear to extend from the nucleus itself around into the 
horn of the crescent. 
In addition to this thick peripheral layer, which I regard as nervous, 
there are in the anal ganglion a few large cells. Some are wedged in 
below the middle portion of the cord like those which have already been 
described. Others may be found in the space between the peripheral 
layer and the cord (Fig. 96), with the process directed ventrad. These 
cells do not as a rule appear to be paired. 
At the extreme posterior end of the cord one finds somewhat different 
conditions. Here there is a mass of large ganglionic cells of varied size, 
closely crowded together, and with their processes (Plate VII. Fig. 90) 
mostly directed forward into the ventral nerve cord. The space between 
the cord and the peripheral layer does not exist, and, curiously, the 
ganglion cells of the latter have nearly always two nucleoli instead of 
one as is usual elsewhere. The relation of the cells and processes is very 
complicated here, and the gradations of size are so fine that with the 
material at my command I was unable to determine the exact number 
of cells, or the plan on which they are arranged. The nuclei of these 
