— III — 
and having dark thickenings at their extremities, near the membrane 
of the nucleus (fig. 42, f) etc. etc. I will, however, pay no more 
attention to these structures, here, as they are probably only pro- 
duced by the nuclei being fixed in different stages of their life; in 
some cases we have even, perhaps, a beginning segmentation of the 
nucleus (fig. 42, e). 
Kepiipops norvegicus. 
In Nephrops, the structure of the ganglion cells is quite similar 
to what we have described of Homarus. In sections, the protoplasm 
of the large cells generally exhibits quite similar light areas, resemb- 
hng vacuoli, and arising from the transsection of bundles or masses 
of primitive tubes. The contents of the nervous processes originate 
in the same manner; a similar spongioplasmic reticulation is present 
in the protoplasm, it being especially visible near the sheaths of the 
cells with which it is intimately united. We can, thus, as regards 
the structure of the ganglion cells of Nephrops, refer the reader to 
our description of the ganglion cells of Homarus. 
The Polychætes. 
Sections of the large ganglion cells of the Nereidce (N. virens etc.) 
exibit, generally, a prominent granular appearance with a distinct 
reticulation extending between and uniting the granules with each 
other, the granules being generally situated at the points where the 
walls of the meshes unite (fig. 43). Some of the granules are very 
large and prominent, and are principally situated in the mesial part of 
the protoplasm. They have, in my preparations treated with fluids 
containing osmic acid and stained with hæmatoxylin, a very dark 
almost black staining, and they consist, I think, of a fattish (myeloid.?) 
substance.^) 
In a great many cells, I observed a difterentiation in the stain- 
ing of the protoplasm, somewhat similar to what is described of the 
cells of Homarus. A disposition to a darker staining of the mesial 
part of the protoplasm is very often observed; besides this the 
larger granules are also, as just mentioned, situated especially here 
which contributes somewhat to a darker appearance (vide fig. 44 
^) Whether the substance of these granules is the same, or has any relation 
to the substance which gives the nervous system of many Polychætes the well- 
known reddish or yellowish staining, I cannot say, as I have not yet very closely 
examined the ganglion cells of the Polychætes in the live-state. 
