PROFESSOR OWEN ON THE AYE-AYE. 85 
curved fissure near the back part of each hemisphere, answering to that marked 7, 
in the brain of the Cat, in my memoir on the Cheetah’, which is wanting in Chiromys. 
The side of the anterior lobe in Stenops appears to have a deeper and better-marked 
vertical fissure, curved with the convexity forward: a few shallow linear indentations 
mark the sides of the narrower anterior lobes in Chiromys. This animal, therefore, like 
the Mongoz Lemur, associates with its superiority of size over Stenops and Tarsius 
a more regular and complex folding of the cerebral superficies. 
In the Squirrels the cerebral hemispheres are devoid of convolutions, and do not 
extend over the cerebellum ; and in the few larger Rodentia, as, e. g., Agouti?, Capybara, 
in which any fissuring of the cerebral surface appears, it is as a feeble trace of the 
medio-longitudinal fissure, and is associated with the depressed form and small propor- 
tion of the cerebrum characteristic of the Lissencephalous group. By the brain alone 
Chiromys is proved to be no Rodent, but might be recognized as a true Gyrencephale, 
and, in that category, as having its nearest affinity with the Lemuride. 
In the absence of the digital eminence and in the restricted development of the back 
part of the lateral ventricle, Chiromys resembles Stenops: its brain shows no indication of 
the linear fissure produced backward from the beginning of the descending horn, which 
Burmeister figures in the brain of Tarsius*. 
The ‘ flocculus cerebelli,’ into which Foville traced the origin of the acoustic nerve, 
is present in most of the timid and sharp-eared Rodents ; but it is likewise present in 
the Stenops and Tarsius*, and is associated, as its presumed function might lead one 
to suspect, with the large external ears and well-developed auditory organ of Chiromys. 
The rhinencephala, or olfactory bulbs, project in advance of the prosencephala in all 
Rodents ; and this appears likewise to be the case with the Tarsius; but Chiromys 
agrees with the higher Lemuride and Quadrumana in the production of the anterior 
cerebral lobes above the olfactory lobes. 
The Viscera.—Iu the following comparison of the internal abdominal and thoracic 
organs of the Aye-aye, I shall restrict myself to the Quadrumanous and Rodent orders, 
and herein to the Lemurine and Sciurine families respectively. in both these families the 
large obtuse blind end of the stomach projects far to the left of the cardia; this orifice 
and the pylorus are approximated ; and the ‘ lesser curvature’ is accordingly very short. 
But the stomach of the Aye-aye more resembles that of Stenops than of Sciurus ; the 
cesophagus is less prolonged in the abdomen than in the Squirrels and most Rodents. 
The cecum presents a point of greater contrast between the Lemurs and the Squirrels. 
In the latter this gut is very long, is narrowest where the ileum enters, and increases 
to its blind end, which is thick and obtuse ; most of the ceecum exceeding in width the 
rest of the large intestines. In the Lemurs the widest part of the cecum is where the 
* Op. cit. pl. 20. fig. 4. 
2 Prep. No. 1323 c, Physiol. Series, Hunterian Collection ; Physiol. Catalogue, vol. iii. p. 29. 
° Op. cit. taf. 6. fig. 15. * Tb. figs. 13, 16. 
