994 
pituitary body (f). These inferior lobes are 
generally of considerable size, of an oval or 
kidney shape, and sometimes, but rarely, con- 
tain ventricular cavities, which communicate 
with the third ventricle, and through it with 
the great ventricles contained in the “ hollow 
lobes ;” they furnish fibres of origin to the 
optic nerves, and it is from the fissure between 
them and the medulla oblongata that the nerves 
of the third pair take their origin. 
Fig. 528. 
Brain of Perch, lower surface. (After Cuvier.) 
Letters a, b,c, g, h, as in preceding figures; e, 
inferior lobes ; f, pituitary body ; i, swelling at com- 
mencement of olfactory nerve ; m, optic nerves; 0, 
olfactory ; p, g, r,s, t, encephalic nerves. 
The pituitary body (fig. 528, f) occupies its 
usual position on the base of the brain at the 
extremity of the infundibulum; it is generally 
of large size in Fishes, and is often connected 
with membranous and vascular appendages of 
various forms,—a circumstance which is, how- 
ever, most remarkable in the cartilaginous 
Fishes. Occasionally, as for example in the 
Lophius and the Haddock, the infundibulum 
is prolonged into a slender filament, and the 
punisey body is removed very far forward ; 
ut the uses of these parts are as problematical 
in Fishes as in the other classes of Vertebrata. 
The cerebellum (figs. 526, 527, a) in osseous 
Fishes is of considerable size, but consists of 
the median portion only, no lateral lobes being 
as yet developed, or at least they are only indi- 
cated by slight eminences. Its shape is gene- 
rally that of a blunted cone, the apex of which 
is bent backwards; but there are instances, as 
for example the Mackarel, in which it is di- 
rected forwards, and sometimes it extends so 
far forwards as to overlap all the rest of the en- 
cephalon. Owing to the deficiency of the la- 
teral lobes of the cerebellum there are of course 
no traces of a pons Varolii. 
Behind the cerebellum, on each side of the 
fourth ventricle, and sometimes even covering 
that cavity, are certain supplementary lobes 
’ (fig. 527, g ) which would seem to be peculiar 
to Fishes, and which are very variable in their 
proportions, forms, and connections. In most 
osseous Fishes they consist of two protuber- 
ances or swellings of the sides of the medulla 
behind the cerebellum, which touch each other 
along the mesial line or are united by a com- 
missure. 
In the Cyprinide their volume is so consi- 
derable that they cover the greater part of the 
medulla oblongata, and their sides are furrowed 
with transverse strie In the Grey Mullet they 
are also very large, and their surface is marked 
with tortuous sulci, giving the appearance of 
cerebral convolutions. It is, however, in the 
Trigle or Gurnards that these lobes are most 
largely developed, amounting in number to as 
PISCES. 
many as five on each side, and occupying a 
space equal in length to all the rest of the 
encephalon, and extending backwards as far 
as the second vertebra. It is from the last — 
of these lobes that the second pair of spinal — 
nerves is given off, which in this genus supplies — 
the free rays situated in front of the 
fins.* 
In the chondropteryginous Fishes the strue- 
ture of the encephalon offers many remarkable — 
peculiarities. Thus, in the Rays and Sharks the — 
proportionate size of the olfactory lobes is enor- 
mous, and instead of simply having a commis- 
sural communication with each other, are 
consolidated into one mass. The hemis 
enclose a capacious ventricle, but there are no 
distinct fibres visible upon its inner surface, 
neither are the representatives of the tubercula- 
quadrigemina of osseous Fishes apparent. The 
cerebellum is of great relative size, but of very 
variable form in different species; and not 
unfrequently it is divided into lamine by deep 
transverse sulci. The supplementary lobes 
behind the cerebellum are represented by folds 
or cords of nervous matter, which are ; 
from each side of the posterior edge of the 
base of the cerebellum and run backwards 
along the margin of the fourth ventricle. A 
The brain of the Tunny ( Thynnus vulg. 
Cuv). is remarkable for the extent of the cer 
bellum, and the complication of the internal 
tubercles. The olfactory nerves are small and 
oval. The hollow or cerebral lobes are of very 
great size, and nearly spherical, with a lateral 
fissure inferiorly. On opening them, instead of 
the tubercles generally met with in Fishes, 
there is found on each side a mass divided into 
three lobes, which are themselves grooved with 
a fissure, so that the whole resembles a cylinder 
or cord having six folds, twelve in all. 
cerebellum is larger than the rest of the ence- 
phalon, and, arising from the medulla oblon 
gata, curves forwards, overlaying both the 
hollow lobes and the olfactory lobes even as fa 
as the anterior extremity of the latter, its bread 
being little less than half its length. At 
posterior part of its base there is on each sid 
a rounded protuberance, different in characte 
from those enlargements which are frequentl 
met with in other Fishes at the commencemer 
of the medulla oblongata. : 
Nervous system.—The olfactory nerves (, 
529 ) arise from the olfactory lobes of the braii 
* The various names applied by different a 
to the different parts described above are calcula 
to create great embarrassment and confusion. Th 
Haller in his ‘ Physiology,” and likewise in_ 
“ Opera Minora,’ calls the lobes (¢, ¢ ) anterior ol} 
tory tubercles, the lobes (e, e) inferior olfactory 
bercles, the hollow lobes (0, 6) optic 7 
M. Arsaki, in his thesis ‘ De cerebro et med 
spinali pisciam,’ calls the hollow lobes (6, 6) tub 
cula quadrigemina, and regards the anterior | 
(c, c) as the representatives of the hemisphe 
M. Weber, in his ‘ Anatomia comparata nervi § 
pathetici,’ whilst he recognizes the hollow 1 
(6, b) as the cerebral hemispheres, regards # 
cerebellum (a) as the analogue of the tuberci 
quadrigemina, and the supplemen lobes 
at the commencement of the medulla oblong 
representing the cerebellum, : 
ba 
