740 
MR. A. SANDERS ON THE ANATOMY OP THE 
is reduced to comparatively small dimensions ; its anterior border is prolonged into a 
body (fig. 1 v.c.), which projects into the ventricle of the optic lobe, and was 
described by Haller under the name “ tuberculum cordiforme.” This is essentially a 
prolongation of the unpaired tuberosity, which passing into the ventricle over the 
aquseductus sylvii, nearly as far forward as the anterior end of the same, is there 
turned back, and reaching the posterior and upper end of the tectum joins the so- 
called fornix. 
In the Carp, which was the species investigated by Haller, the lateral portions 
or aloe (figs. 4 and 5, a.v.c .) of this body are highly developed, and form several 
folds, the sum total of which were termed by that anatomist “ cornu ammonis,” pro- 
bably from their form, and not as compared to the part of the same name in the human 
brain. This cornu ammonis is found considerably developed also in Crenilabrus, where 
it fills the whole cavity of the ventricle of the optic lobe. 
It is probably the enormous development of this part which forms the extraordinary 
structure in the brain of Mormyrus Cyprinoides (Nilhecht), described by Ecker (47) 
and by Marcusen (51), and later by Oeffinger (57). Marcusen thought that it 
was most probably the cerebellum, and Miklucho-Maclay supports that idea. As I 
have never had the good fortune to meet with specimens of this fish, and as the 
authors just mentioned do not touch upon the microscopic anatomy (except Mar- 
cusen, who does not do so very minutely), I am unable to give a decided opinion ; 
but I should think that it w 7 as not the cerebellum precisely, with which this remarkable 
structure homoJogised, but that part of it which goes under the name of the valvula 
cerebelli. Of course this opinion is a mere guess, but the inspection of a few thin 
sections of a fresh subject would soon decide the point. 
Weber’s was one of the few exceptions to the generally received opinion that this 
lobe is the cerebellum; in his first paper (17) he termed it “ corpus quadrigeminum seu 
Impar Majus,” but subsequently he changed his views, and denominated it “ vorderer 
unpaar Hugel des Ivleingeliirns ; ” while that part of the medulla oblongata which 
covers over the narrow part of the fourth ventricle behind it, and which in some species 
is developed into a distinct tuberosity, and which Haller named “pons mammillaris,” 
Weber termed “Hinterer unpaar Hugel des Kleingehirns.” Mayer (49) followed his 
opinion; his name for this part was “ epiencepbalon seu cerebelli lobus anterior,” but 
he differed from Weber in placing his “cerebelli lobus posterior” in the pair of tuberosi- 
ties on the dorsal side of the medulla oblongata, from which the nervi vagi take their 
origin. These tuberosities are situated on the dorsal side of the medulla oblongata 
behind the cerebellum. They enclose between them a deep fissure, which corresponds 
to the posterior part of the fourth ventricle. Anteriorly in some fishes they are united 
together in the midline by a single tuberosity, which is situated over the narrow part 
of the fourth ventricle, immediately behind the crura cerebelli. Usually this tube- 
rosity is replaced by a thin layer of granular substance occupying the same position. 
Miklucho-Maclay ( 62 ) has within the last few years attempted to place the 
