936 
MR. A. SANDERS ON THE ANATOMY OF THE 
form more than a small tuberosity bridging over the fourth ventricle. It resembles, 
however, the form of the cerebellum in Fishes of the family Siluridse, of which Schilbe 
Hcisselquistii, found also in the Nile, may be taken as an example, but in comparison 
to the size of the brain it is much smaller, since in S. Hasselquistii it predominates 
over the other lobes in size, while here it is overshadowed and compressed by the 
enormous size of the wings of the valvula cerebelli. In structure it agrees with 
that of the cerebellum in all Yertebrata. 
Denissenko*, in his interesting paper on the anatomy of this lobe, divides it into 
three layers, viz.: the molecular, which is external; the granular coming next, and the 
fibrous occupying the centre of the lobule; but MeyneetI makes a separate layer for 
the Purkinje cells, which is more in accordance with the state of affairs in the Teleostei; 
I have never found these cells so irregularly dispersed through the molecular layer in 
those Fishes which I have examined as is described by Denissenko. The nerve fibres 
also do hot form a distinct layer, except quite at the root of the organ. 
Adopting Meynert’s idea, I shall therefore speak of the Purkinje cells as forming a 
distinct layer, and term it the intermediate layer. 
Thus we have in the cerebellum of the Mormyrus three layers, counting from the 
outside towards the centre, viz. : the molecular, the intermediate, and the granular 
layers ; the fibrous layer may be looked on as part of, and diffused through, the last 
mentioned one. These correspond to the first three layers in M. cephalus, and the 
fibrous stratum in the parts where it forms a distinct layer would in like manner 
correspond to the fourth. 
The radial striation which characterises the molecular layer is very strongly marked 
in this species. This appearance is caused by prolongations from the single layer of 
epethelial cells which cover the whole surface of the cerebellum; each cell sends a 
process for a considerable distance into this layer. StiedaJ has published a good 
description of these cells, to which he has given the appropriate name “ stiftzelle;” 
Boll§ showed how they were developed from the so-called “ Deiters,” or connective 
tissue cells, so as to form a membrane beneath the pia mater. These peculiar cells 
appear to exist on and form a covering for most parts of the brain, e.g., the 
cerebrum, and the tecta lobi optici, but they do not form such well marked and 
distinct striations in other organs as they do in the cerebellum. This layer is not 
formed entirely of connective tissue, although these processes do occupy a considerable 
part of it, and cause the striated appearance which gives it such a characteristic 
aspect; there is a large quantity of molecular matter as well as small cells in it. These 
small cells are extremely scarce, although occasionally met with; they resemble the 
cells of the granular layer, and have a nucleus and a nucleolus, which latter is a mere 
* Znr Frage ii. den Ban der Kleinhirnrinde, &c., Arch. f. Mikroskopisce Anatomie, Bd. xiv., 1877. 
f StrickeiVs Handbook, Sydenham Society, yoI. ii. 
jt Stndien ii. d. Centralnervensystem der Wirbelthiere, p. 154. 
§ Loc. tit. 
