The hippocampus minor, as in man, corresponds, on the surface of the Chimpanzee's brain, with the upper of the two deep hidden sulci at the bottom of the fissure of the hippocampus; and the eminentia collateralis with the lower of those sulci. Hence, as already deduced from other considerations, even the presence of this fissure, without its sulci and the corresponding projections into a posterior cornu, would suffice to identify corresponding parts of the cerebral hemisphere. The remaining points, which seem worthy of notice, are the following. The hippocampus major corresponded to a thick rolled convolution and sulcus; its lower end, fig. A, d′ was much expanded, and, what I shall call, to avoid confusion, its convex border was twice, though feebly, indented. The fascia dentata was quite distinct. Of the corpora quadrigemina, the upper pair were the larger, but the less prominent. The pineal body was large, soft, and contained no gritty particles. The habenulæ were distinct. The pituitary body was large, and wider than deep. The corpora albicantia were beautifully seen, quite distinct from each other, and connected, as in man, with the anterior pillars of the fornix. On the medulla oblongata, the corpora olivaria were neatly defined and of good size; and the decussation of the pyramids was very prettily seen. In some of these points Macartney's description is not quite correct.
Lastly, all the parts of the cerebellum, so far as I have yet examined them, are the same as in the human encephalon; only the lateral hemispheres are wider and flatter. I have still preserved this and also the left half of the brain, on which I propose some day to follow the arrangement of the fibres.
I may be permitted to add, in conclusion, that my sole object in this paper has been to record the results of an anatomical investigation. I have no theory, zoological, or physiological, to support; I have no leaning towards any of the developmental hypotheses of the origin of species. But, on the question of facts, and the interpretation of those facts, my results, as to the existence of a posterior lobe, of a posterior cornu, and of a hippocampus minor, in the Chimpanzee, will be found to harmonize with the investigations and conclusions of Prof. Huxley and of Prof. Allen Thomson, already published in this Review.
Description of the Figures in Plate VI.
Fig. 1. Under view of a plaster cast of the interior of the Chimpanzee's skull, taken before the membranes were removed from the base; (from a photograph.) F F, frontal lobes of the cerebrum; T T, temporo-sphenoidal lobes; O O, occipital lobes; V, pons Varolii; M, medulla oblongate; C C, cerebellum.
Fig. 2. Under view, or base of the Chimpanzee's brain, hardened in spirit, with the pia mater and arachnoid taken away. Intended to show the displacement of the parts, especially of the cerebellum, from their natural positions; (from a photo-
