108 MR. FLOWER ON THE BRAIN OF THE JAVAN LORIS. 
A second character by which the Lemurs are distinguished from the Monkeys is the 
large size of the olfactory lobes: but in these portions of the encephalic mass a gradual 
increase may be perceived from the higher to the lower Quadrumana ; and they project 
in front of the cerebral hemispheres in all the Platyrhini, and even in the greater 
number of the Old World Apes. In the large majority of Mammals the base of these 
lobes extends backwards to the under surface of the temporal lobe, obliterating the 
lower part of the fissure of Sylvius ; whereas in the true Apes, and in Man, their con- 
nexion with the cerebral hemisphere is chiefly: with the anterior lobe and the bottom of 
the fissure itself. In this respect, as well as in the size of the lobes, Stenops and Lemur 
hold an intermediate position between the two groups, more nearly approaching the 
higher than the lower type. 
Another most distinctive characteristic of the primatial brain is the possession of a 
complete Sylvian fissure. Although the presence of this important sulcus is not 
recognized by some anatomists in the Mammalia generally, it exists almost throughout 
the series, but in a rudimentary condition, the part which remains corresponding to 
the middle portion of the fissure when completely developed. Concealed by the lips 
of the Sylvian fissure is the median lobe—so well marked and even complex in Man, 
simpler and smaller, but still distinct, throughout the greater part of the Monkey series, 
but lost in the diminutive Marmoset, recognizable, however, in the Lemur, not dis- 
tinctly traceable in S/enops, absent in all other Mammalia. Next to the fissure of 
Sylvius, the most characteristic Simian sulcus on the outer surface of the hemisphere 
is the one placed behind and parallel to it—the antero-temporal, the last that disappears 
as the size of the brain, and attendant amount of surface-involution, decreases. In the 
presence of this sulcus both Stenops and Lemur perfectly agree with the type. After 
this the most persistent fissure on the outer face appears to be the one bounding the 
upper border of the angular gyrus; this also exists in Lemur, but is not seen on the 
smaller hemisphere of Stenops. 
But it is perhaps the sulci of the inner face of the hemisphere that are most cha- 
racteristic of the Primates, and offer the most striking differential features from the 
other Mammalia. Here, too, the Lemuride follow strictly the higher type. That 
essentially primatial sulcus, the calcarine, which persists deeply marked in the little 
Hapale iacchus, when every other trace of fissure, except the Sylvian, is gone, is equally 
well developed in both Lemur and Stenops. The calloso-marginal is also well marked, 
but a fissure somewhat corresponding to this is found throughout the Mammalia. 
In order to make a comparison of the brain of the Lemuride with those of the 
higher Quadrumana more perfect, brains of somewhat similar size in the two groups 
should be selected ; and in reference to such a comparison, as well as on other grounds, 
it is to be regretted that we are not yet sufficiently acquainted with the cerebral 
organization of many of the Platyrhine Apes; but among those that are known there 
are two which, in general arrangement of sulci, present great resemblance to Lemur 
