258 PROF. HUXLEY ON THE [June 1), 



presents one or two minor sulci upon its surface, and has its inner 

 edge notciied by the upper end of the calloso-marginal sulcus. The 

 temporal lobe, again, is plainly divided into the usual antero-tem- 

 poral, medio-temporal, and postero-temporal gyri, and the occipital 

 lobe has a horizontal sulcus which marks off an infer-occipital gyrus 

 from an upper region representing the super- and medi-occipital 

 gyri. In both brains I find a distinct occipito-temporal sulcus (scis- 

 sure perpendiculaire externe), though M. Gratiolet states that this 

 very Simian fissure is obliterated in Ateles {I. c. p. 76). However, 

 he figures what I cannot but consider to be this sulcus in his pi. 10. 

 f. 2. 



Another point on which 1 am much inclined to differ from M. 

 Gratiolet is that which he himself regards as a difficulty — viz. the 

 extent of the fissure of Sylvius. I cannot find the " pli interm6- 

 diaire, tres petit il est vrai," which he supposes (/. c. p. 75) to bound 

 the upper extremity of the Sylvian fissure. On the contrary, it ap- 

 pears to me to be one continuous sulcus ; and admitting this to be the 

 case, it will not be longer than the Sylvian fissure of the Douroucouli 

 (Gratiolet, pi. 11 . figs. JO, 11). But if this be the fact, then 6, fig. 4, 

 will be the angular gyrus (pli courbe) and 14, fig. 4, will be the 

 second anuectent gyrus (deuxieme pli de passage). 



This interpretation, again, would diverge from that given by M. 

 Gratiolet ; but I must confess that, to me, the least satisfactory part 

 of this able observer's treatise is that which relates to the identifica- 

 tion of the angular gyrus and the anuectent gyri, throughout the 

 series of the Primates. 



The transverse diameter of the cerebellum (PI. XXIX. figs. 4, 6, 7) 

 is much larger, in proportion to its antero-posterior measurement, 

 than in Man, and the sides of the upper surface slope more away 

 from the vermis superior. The anterior and posterior notches are 

 almost obliterated, the posterior extremity of the vermis extending 

 very nearly as far back as the level of the posterior edges of the 

 cerebellar hemispheres. The transverse diameter of the vermis is 

 .much greater, in proportion to the whole diameter of the cerebellum, 

 than in Man, and the vermis inferior presents no such sharp distinc- 

 tion into pyramid, uvula, &c., as in the human subject. The great 

 horizontal fissure is distinct and tolerably deep ; but I could discover 

 no definite minor fissures, and consequently no demarcation of the 

 upper, or under, surfaces of the hemispheres into lobuli. There are 

 not even any distinct lobules, as amygdala, beside the uvula. On the 

 other hand, the flocculi are enormous, and end in prominent rounded 

 processes, which fit into deep fossae upon the inner surfaces of the 

 petrosal bones. 



A distinct posterior medullary velum was visible on each side, 

 connecting the nodule with the flocculus ; and the valve of Vieussens, 

 as usual, united the processus e cerebello ad testes. The arbor vitae 

 was well-marked and complex in its branchings, in a vertical median 

 section of the cerebellum. 



Of the corpora quadrigemina the nates are smaller than the testes ; 

 but the brachia superiora are larger than the brachia inferiora, on 



