292 
hemispheres are 
enetrated by an- 
ractuous fissures. 
In the Wombat 
a large longitudi- 
nal fissure bounds 
the outer side of 
the natiform pro- 
tuberance | ol- 
factory tract at the 
base of the brain ; 
from the anterior 
moiety of this fis- 
sure three or four 
smaller ones curve 
upwards upon the 
sides of the hemi- 
spheres. On the 
upper surface a 
short transverse 
fissure marks off 
what may be regarded as the anterior lobe 
of the cerebrum, and behind this each hemi- 
sphere exhibits a few detached shallow fissures. 
In the Kangaroo (fig. 115) these fissures be- 
come continuous and are deeper; a long 
and nearly transverse anfractuosity divides the 
upper surface of the hemisphere; behind the 
shorter fissure which marks off the anterior 
lobe, and between the two transverse fissures 
there is a longitudinal one bounding a con- 
volution that runs parallel with the median 
interspace of the hemispheres. The ante- 
rior lobes are also broken by small fissures; 
two or three long and moderately deep 
ones ascend upon the sides of the hemi- 
spheres (a), and the posterior portion (6) 
preter occasionally small detached fissures. 
o far therefore as the external surface is con- 
Brain of Dasyurus ursinus. 
Fig. 115. 
Brain of Macropus major. 
MARSUPIALIA. 
cerned, the brains of the herbivorous Marsu- _ 
pials are more complicated than those of any — 
of the Rodent Mammalia. The cerebellum 
llel, trans- _ 
presents the usual close-set, sub- 
verse convolutions: it is remarkable for ¢ 
large proportional size of the median or 
form lobe, as compared with the lateral le 
especially in the carnivorous and insecti 
Marsupials, where this condition is a: 
with a corresponding diminution of their com= 
missural band or ‘ pons Varolii,’ as is shown ii 
the view of the base of the brain of an Ope 
sum (fig. 116, 6). am 
(M8 ) In the Kangaroos, 
Perameles,Phalanger k 
and Koala the hemis- 
pheres or lateral lobes 
of the cerebellum at 
characterized by asm: 
subspherical late: 
process or apper 
(¢, ¢, fig. 115), 
is lodged in a pec 
fossa of the peti 
bone above the in 
me 
——— 
Opossums, but they 
Brain of Didelphys Vir- ate not developed” 
giniana. t . n the 
upper surface of the 
cerebellum the medullary substance appears 
superficially at a small tract between the ver= 
miform processes, marked with an asterisk in — 
figures 115 and 117. The simple disposi- 
tion of the arbor vite is shown in fig. 118, _ 
Behind the pons Varolii are seen the two 
trapezoid bodies (c, fig. 116); and the corpora — 
pyramidalia (d) are always pep in 
guishable from the corpora olivaria. 
cerebri, which, in the um (e, fe 116 r 
left exposed below, like the optic lobes abe 
by reason of the small proportional size of 
cerebrum, are more completely concealed in tl 
brain of the Kangaroo and Wombat. Then: 
form protuberances form a great 
the under part of the cerebral hemisphere 
all the Marsupials; their external bour 
which is basial in the Wombat and Kangaro 
runs along the side of the hemispheres t 
outer side of the olfactory lobe in the Ope 
be inner root of the olfactory =e orms: 
ulbous or lionic enlargement a 
* b). Behind the comnnienene of ie optic 
nerves is seen a broad and short infundibulum 
supporting the pituitary gland (d, fig. 1 
and posterior to this is the single corpus 
cans. The optic lobes are solid, and are each 
divided by a transverse fissure, as in the Pla- 
cental Mammalia; the anterior divisions or — 
‘nates ’ (B, fig.117) have a greater longitudinal 
diameter than the posterior ones or ‘ testes,’ 
which have a greater transverse development. _ 
The difference in the relative development of 
the nates and testes is much less in the herbi- 
vorous and carnivorous Marsupials than in the 
corresponding Placental quadrupeds. 
- 3 
HOTUOen | 
