194 
ME. W. H. FLOWBE ON THE POSTEEIOE LOBES 
sweep upwards. It penetrates deeply into the lobe, not quite to the same extent as in 
Cercopithecus, but is so disposed as to contain a similar convolution. 
Hapale jacchus, the Common Marmoset. — In an adult specimen which died at the 
Zoological Society’s Gardens, September 25, 1861, the brain was exposed in situ by chp- 
ping away different portions of the cranial bones, and the drawings (Plate III. figs. 8 & 9) 
made before its outline had been altered by removal from its bed in the skull. Seen 
from above, the two hemispheres form an elongated oval, slightly narrowed anteriorly. 
The olfactory lobes extend forwards beyond the cerebrum, but no part of the cere- 
bellum is seen. The side view shows the elongation and flattening of the whole hemi- 
sphere, and the extent to which the posterior lobes project beyond the cerebellum. 
The orbital region of the anterior lobe is greatly excavated. The fissure of Sylvius is 
well marked, but on separating its lips no distinct median lobe is seen, the only indi- 
cation of it being a very slight elevation of the floor of the middle third of the fissure. 
The outer surface of the hemisphere is perfectly smooth and free from sulci, a faint 
depression only occupying the situation of the antero-temporal, the most persistent of 
all the sulci of the outer face in the Quadrumana. 
The inner surface of the hemisphere (Plate III. fig. 10), quite smooth in its anterior and 
superior portions, presents, nevertheless, three distinctly marked sulci, the dentate {m\ 
the collateral (%), and, occupying exactly the same situation as in the higher Primates, 
the calcarine sulcus (/). This is quite simple, not bifurcated at the end, or joined by any 
other fissure, and describes a curve with the convexity upwards. There is no trace either 
of the occipito-parietal or the calloso-marginal sulcus, A section made at the middle 
of the posterior lobe (corresponding to the section B in the larger brains) shows that the 
calcarine fissm’e is of great depth and has a downward curve. The grey matter sm*- 
romiding it occupies nearly the whole of the interior space of the lobe, forming a hippo- 
campus minor of simple construction, but very great relative size. The very narrow 
stripe of medullary white matter between this involution and the external surface con- 
tains a distinctly marked crescentic opening, the section of the posterior cornu. 
A horizontal section through the left hemisphere (Plate III. fig. 9) exhibits the great 
length of the posterior lobe as compared with the antero-median, viz. as 62 to 100. 
The posterior cornu in this \iew describes a regular curve, with the concavity inwards, 
and is seen to extend to within i^th of an inch of the apex of the hemisphere. Its 
walls fell apart directly the section was made, and there appeared to be a distinct iiniug 
membrane, on which fine blood-vessels were seen to ramify. 
The above description would apply almost equally well to the brain of H. oedipus, two 
examples of which have been dissected. 
Thus, in the brain of these diminutive creatures and in that of Man, placed at oppo- 
site ends of an extensive series, and in many respects so widely removed from each 
other, are found certain well-marked common characters in the posterior lobes ; and the 
principal distinction that we can draw between them, with respect to this portion of the 
brain, is, that in the Marmoset the whole lobe is more elongated, the calcarine fissm'e 
