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and 45). There is generally no distinct demarcation betwen the 
deeply stained mesial part of the protoplasm and the lighter pe- 
ripheral layers; sometimes, however, such a demarcation is present, 
the lighter stained substance being peripherically situated in various 
more or less distinctly defined masses (fig. 44). Small bundles of 
primitive tubes, similar to those which are often present in the 
ganglion cells of Homarus and Nephrops, I have not generally ob- 
served in the ganglion cells of Nereis. The contents of the nervous 
process seems generally to originate in a gradual convergence of 
primitive tubes in the protoplasm, towards the pole where the pro- 
cess originates (cmfr. fig. 43). Sometimes, I believe to have observed 
the contents of the nervous process passing as an undivided, lightly 
stained bundle for some distance into the protoplasm ; consequently, 
a structure somewhat similar to what is above described in the 
ganglion cells of Homarus. 
A spongioplasmic reticulation quite similar to the peculiar re- 
ticulation in the ganglion cells of Homarus does not occur in Nereis, 
so far as our experience goes, at all events not to such an extent. In 
some cells, I haVe, however, observed spongioplasmic fibres issuing 
from the neuroglia-membrane enveloping the cell and penetrating 
into the protoplasm (vide fig. 43, sf and fig. 44, sf)\ probably con- 
tributing to form the reticulation already described. 
A question of great interest is, whether the reticulation, seen in 
the sections of the cell-protoplasm of Nereis is a real reticulation 
or only an appearance produced by transsection of primitive tubes .^^ 
I feel most disposed to believe that the latter is the case. Strange 
to say, neither longitudinally transsected primitive tubes, nor a 
concentric striation are as often seen in the ganglion cells as we 
could expect if all meshes were transsected primitive tubes; some- 
times we can, however, observe longitudinally transsected tubes in 
the protoplasm, and the reason why they are not oftener seen is, 
perhaps, because they have a very curved and complicated course. 
The nuclei of the ganglion cells have, in the Nereidæ, a 
similar structure as those of Homarus. They have a distinct sur- 
rounding membrane, inside which a reticulation is extended; in this 
reticulation dark granules are situated, generally at the points where 
the fibres forming the meshes unite. One or sometimes two nucleoli 
are seen, and sometimes no distinct nucleolus is present, but only 
largish granules are spread m the reticulation (vide fig. 43, 44, 45). 
The situation of the nuclei in the protoplasm is generally diffe- 
rent from what it is in the ganglion cells of Homarus. The nuclei 
