— 37 - 
une substance visqueuse, épaisse, granuleuse et tres malléable.« 
About the Oligochætes he says: »Les ceUules nerveuses .... sont 
formées par une substance demi-liquide visqueuse, excessivement mal- 
léable, peu granuleuse. Elles contiennent un noyau réfringent ho- 
mogene et granulations graisseuses situées å son voisinage.« 
If we look through the modern literature having reference to 
the invertebrate nervous system, and compare the many different 
views of the structure of the ganglion cells, we meet with a con- 
fusion on the subject which is far from encouraging. Some writers 
distinguish between granulous cells and homogeneous ones, other 
writers believe in a concentric striation, or even a longitudinal 
striation (Rohde). ^) 
Some writers distinguish between ganglion cells w^ith a process 
originating in the nucleolus (/^Kernkorperfortsåtze«), or nucleus and 
cells with a process originating in the protoplasm (»Protoplasmafort- 
såtze«). Others, e. g. Haller, describe cells having both kinds 
of processes. A great many writers however deny, or doubt, any exis- 
tence of processes originating in nucleoli or nuclei, etc. etc. All these 
distinctions and differences of opinion exist, although we certainly 
must feel inclined, a priori, to suppose that there must be uniformity, 
to some extent, through the whole animal kingdom in this respect, 
and that the differences must have arisen in the development of less 
complicated structures to more complicated ones. 
1) In E. Bohde's paper on the Nematodes (1885) we meet with a descrip- 
tion of the structure of the ganglion cells which is of a somewhat peculiar kind. 
The writer describes ganglion cells having different modes of striation, a radiate 
striation, a concentric one, and a longitudinal one (1. c. p. 16 — 17; fig. 14 — 34.) 
As I have not examined the nervous system of the Nematodes I can not, of 
course, deny the correctness of this statement; if I may judge, however, from the 
results of my investigations on other animals, I feel inclined to believe that these 
descriptions are caused, at all events partly, by optical illusion. 
It may here, also, be mentioned that Yung (1878) describes a longitudinal 
striation of the protoplasm of the ganglion cells of Astacus as being a post- 
mortem appearance produced by the influence of acids (picric or nitric acid — 
1. c. 1878, p. 424 — 425). In the fresh state he describes the cells as having »un 
contenu liquide absolument identiques å celui des tubes nerveux å Vétat frais.« 
The American scientist PacJcard gives a very strange description of the 
ganglion cells of Asellus (1884), he says that they «have not, as in the brain of 
the lobster, a simple nucleus and nucleolus, but they usually have numerous, from 
10 to 20, nuclei, the nucleolus of each nucleus readily receiving a stain and forming 
a distinct dark mass.« How this description is to be explained I certainly can not 
tell; he does not mention the structure of the cell-protoplasm. 
