Prentiss, Weurofiirillar Structures. 169 
process were obscured by longitudinal fibrillae; they cross irreg- 
ularly, but whetker a network was formed could not be deter- 
mined with certainty. 
In the crayfish was found one case of apparent connection 
between the dendrite of a large motor neurone and a longitud- 
inal connective fiber (Figure 12, Plate VI). To economize 
space only a portion of the collateral 2 is shown im the figure, 
but in the preparation this collateral was traced into connection 
with a motor ganglion cell 46, one of the end branches of the 
collateral 2, may be observed uniting with the small longitud- 
inal fiber dat the pointc. This fiber contains several neuro 
fibrillae, while 4, if not a single fibril, is composed of not more 
than two. 4 does not branch on uniting with a, but can be 
traced a short distance toward ¢, the anterior end of the longi- 
tudinal connective. In the preparation, d was seen to extend 
in both directions beyond the limits of the ganglion; naturally, 
its cell was not demonstrated, but the fact that it is much larger 
than 6 is sufficient ground for believing that all of the neuro 
fibrillae which it contains do not come from the nerve element 
a. The connection between 4 and dat the pomt ¢ seems as 
Certain as if they were the branches of a single neurone. 
Fibrillar Netwerks mm the Neuropil. 
A considerable number of cases of fibrillar networks occur- 
ring in the neuropil of Hzude have been described in another 
paper (PRENTisS, : 03); two additional examples of the types 
which occur most frequently in Hirvude, are figured here. Often 
only two or three meshes are formed with which two or three 
fibrillae are connected (Figure 6, Plate V). In other cases the 
networks are much more complex, as seen in Figure 8. These 
examples were found near the center of the neuropil, and there 
is little likelihood of their being mistaken for networks m the 
cell processes. In every instance they were of lmited extent, 
and comparatively few fibrillae were connected with them. 
In Astacus more extensive networks may be demonstrated 
in the neuropil by means of methylen blue. Figures 9 and 13 
are good examples of these fibrillar structures. The meshes 
