— I07 — 
mesial part, but has distinctly defined light masses in its peripheral 
layers (fig. 38, A), or in which plenty of distinct, lightly stained 
bundles, or small masses, of primitive tubes occur (fig. 25). 
There is evidently a great variety in the structure of the proto- 
plasm, as well as in the origin of the nervous process in the ganglion 
cells. I do not think, however, that this difference of structure can 
have any deep physiological significance, because we find every 
stage of transition from one form to another. The peripheral con- 
stituent of the protoplasm in all cells, is evidendy the primitive tube. 
The small circular meshes v/hich are found in sections, every where 
in the protoplasm, in the deeply stained as well as in the lightly 
stained parts, are probably only transsected primitive tubes which 
in the deeply stained parts of the protoplasm are more separated 
from each other by thicker layers of a deeply stained substance 
than they are in the light parts. 
Where, and how, the primitive tubes terminate, or rather how 
they originally are formed, I cannot say. 
In a few cases I have, in the peripheral parts of some cells, 
believed to see slender tubes pass to the enveloping neuroglia-sheath. 
This appearance can, however, also be occasioned by the above 
mentioned spongioplasmic fibres issuing from the sheath. If such 
radiating tubes were really present in all ganglion cells, we could, 
perhaps, easily understand the statement of Dr. Rawitz regarding 
the ganglion cells of the Acephales; viz. that hyaline small pearls 
were exuded from the cells on pressure. These pearls consist, I 
think, of hyaloplasm, and are probably exuded from primitive tubes, 
which must either terminate in the envelope of the cell or must 
have been broken by the pressure. 
If we now consider what we have learnt of the protoplasm of 
the ganglion cells, we may sum it up in the following results: 
The cell-protoplasm is composed of primitive tubes consisting of 
liyaloplasmic contents and spongioplasmic envelope, — further, of a 
spongioplasmic reticulation, extending through the protoplasm and 
also intimately connected with the surrounding cell-sheath — and, 
finally, of a hyaline substance having much resemblance to the hyalo- 
plasm of the primitive tubes. 
The primitive tubes circulate, as we have seen, in the proto- 
plasm, giving it often a concentrically striated appearance (fig. 23). 
In large ganglion cells they are frequently united into a number 
