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 Assuring 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 Leinuridce. 



In the absence of the digital eminence and in the restricted development of the back 

 part of the lateral ventricle, CAiromys 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 LemuridcB and Quadrumana in the production of the anterior 

 cerebral lobes above the olfactory lobes. 



The Viscera. — In 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 

 oesophagus is less prolonged in the abdomen than in the Squirrels and most Rodents. 



The caecum 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 csecura exceeding in width the 

 rest of the large intestines. In the Lemurs the widest part of the caecum is where the 



' Op. cit. pi. 20. fig. 4. 



' Prep. No. 1323 g, Physiol. Series, Hunterian Collection ; Physiol. Catalogue, vol. iii. p. 29. 



" Op. cit. taf. 6. fig. 15. ' li. figs- 13, 16. 



