930 
MR. A. SANDERS ON THE ANATOMY OE THE 
In order to obtain an idea of the brain of a Mormyrus, we may take that organ of 
any ordinary Teleostean, and imagine a fungoid growth taking place from the region 
in front of the cerebellum; we may then imagine this growth to burst through the 
tecta lobi optici, forcing them asunder, repressing them to the basal part of the brain, 
and then to spread out in all directions, covering over and concealing everv one. of the 
remaining portions of the brain. 
We have thus a stalk or peduncle on each side of the region referred to above, and 
expansions which take the form of wings growing in every direction—forward, upward, 
outward, and backward—until the obstacle of the walls of the skull is encountered, 
when, growth still continuing, foldings in various directions occur : thus the anteriorly 
directed wing turns backward on itself on reaching the front extremity of the cranium, 
the dorsal wing turns inward on attaining the roof of the skull, the outer wing turns 
upward under the same condition, while the posterior wing ends in a free edge directed 
backward. This is the state of affairs in the young animal, but as age creeps on the 
complication in the folding of these wings increases. Another lobe becomes developed 
between the outer and the ascending wings ; this also projects forward between the 
anterior wings of each side ; the posterior wing now becomes folded into a number of 
small transverse convolutions, and the dorsal wing develops an additional fold at its 
upper extremity. 
Marcuses"* tried to found genera partly on the greater or less extent of these 
wings, but this arrangement, so far as it is based on the nervous system, will not hold 
good; because even in species with the most highly developed brain, the more simple 
arrangement prevails in young specimens. 
Each wing is provided on the outer side with numerous excessively fine parallel 
ridges, whose structure will be described presently; these ridges follow every curve 
and inequality of the surface, so that their sections present various appearances. 
The consequence of this arrangement is that those parts of the wings which are 
turned back or folded show only the layer of medullary fibres, and are therefore white, 
while the parts which are not reflected, such as the posterior wing and the upper part of 
the dorsal wing, show the minute ridges which give these portions a pinkish colour in 
the fresh state, and cause the minute striations which gave occasion to the comparison 
with the convolutions of the cerebrum of Mammalia; we shall see presently that they 
have nothing to do with these convolutions, but that in fact, they belong to quite 
another part of the brain. 
I have not given figures of the external aspect of the brain of the Mormyridw, 
because Marcus EN’st illustrations are very good, although his drawings of the sections 
and of the microscopic anatomy leave much to be desired. 
Log. cit. 
t Log. cit. 
