-AIOIJI'IIOLOGV OK THE BKAIX IX Till; .Al A .\| .M.\ JJA. 



;3fi7 



Tilt; hrain of JI<'[ial<i(l<iit/.s must ho. i-egurded as the extreme Ibi-in resulting' from those 

 retroijjressive changes which aifect the brain in all the IVosimiu'. As one of the m;iny 

 indications of this, there is the fact, already emphasized by Forsyth Major, that the bi'.-iin 

 of (ilohilemur is distinctly larger and much richer in sulci tiian tliat of Jfcgaltidapis, in 

 spite of the fact that the brain of tlie latter should, iu accordance wilh the laws wiiich 

 regulate the siz(> of the hi-iin, be much the lari^er, Incause Jfrf/al/xhf/t/.s- is Iwice the size 

 of GlohilcmKr. 



The general appearance of the latter is distinctly pitlu^coid, whereas the brain of 

 Megaladapi.s most nearly resembles those Lemurs, such as the ludrisina; and CItiruniijs, 

 the brains of which are least Ape-like. 



TuE Cerebral Hemispheue ix Tarsius axj) the rROsiMi.E gkneralia'. 



'J'lie hemispheres of Tdrshi.s assume a peculiar shape, quite unlike that of any other 

 mammal, being flattened in an extraordinary manner. A maximum depth of lO-') mm. 



Fie. 44. 



Fig. \'i.- — '['arsius s/mlriim. The duisal Mspect of (he liraiii. x 2. 



Fig. 44. — Tarsius spectruyii. The ventral as])ect of the brain. X -. 



Fig. 4.5. — Tarsius spectrum. The left lateral aspect of the hrain. X'at. si/.o. 



in a hemisphere wliich is 16'5 mm. long and 95 mm. broad may seem to stultify this 

 statement ; but it is so deeply excavated in part of the region of greatest depth by an 

 vmusually extensive orbit and behind it by a deep fossa for the corpora (piadrigemina 

 and cerebellum, that it becomes converted into a thin irregular plate. 



In a vieM' of the dorsal surface of the brain, the cerebrum hides all the rest of tin- 

 organ except the caudal margin of the cerebellum and its strongl}- projecting floccidar 

 lobes and olfactory bulbs (tig. 43). 



The unusually extensive orbital excavation of the ventral surface of the licmis])hcres — 

 involving much more than the area usually called " orbital '' — gives to the basal aspect 

 of the brain an appearance spuriously resembling that of most birds, in which large eyes 



SECOND SERIES. — ZOOLOGY, VOL. VIII. 51' 



