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Show 1899.] DE. A. KEITH ON THE CHIMPANZEES. 309 Darwin's point appears more frequently in the Gorilla than in the Chimpanzee. It appears in 9 per cent. Chimpanzees and 26 per cent. Gorillas, the last figure corresponding to its appearance iu M a n - taking an average of various races. The development of the ante-helix in the Gorilla approaches that of M a n more nearly than the Chimpanzee. The muscles of the ear are more rudimentary in the Gorilla than in the Chimpanzee. Almost in every point the ear of the Gorilla is the more human of the two. The external ear is certainly an aid in distinguishing between the Chimpanzee and the Gorilla. 8. The Circulatory and Digestive Systems of the Gorilla and Chimpanzee. Our knowledge of these systems in the two African anthropoids is founded on a too limited amount of material to allow of any definite statement being made as to the points on which they differ. On the whole, they appear to resemble each other very closely. The only feature that appears to demarcate them is seen in the liver. The right lobe of the Gorilla liver shows always a deep fissure, separating off a right lateral lobe, a fissure which occurs vary rarely in the Chimpanzee and only occasionally in the Orang. The liver of the Gorilla, in its division, is the most primitive form found in the Anthropoids and most nearly resembles that of the lower Catarrhini. On the other hand, especially in its bulbous glans penis, the genital system of the Gorilla is the more human. Laryugeal sacs occur both in the Gorilla and Chimpanzee, and it is rather strange that " Johanna " has never been observed to manifest its presence. 9. Hairs and Pigment as distinctive Features of the Gorilla and Chimpanzee. Neither the colour nor arrangement of hair, nor the degree to which the skin is pigmented assist much in the differentiation of the adult female Chimpanzee and Gorilla. In Anthropopiihecus niger the pigment appears much later than in the other Chimpanzees, and circum-oral and supra-orbital parts of the face appear never to become deeply pigmented. The skin of the Gorilla, especially the face, ears, palms, soles, and dorsal aspects of the trunk and limbs, are deeply pigmented at birth. The adults of A. calvus and A. kooloo-kamba show an equally intense deposit of pigment; so does the Central-African variety, but it is unlikely they are so deeply pigmented at birth. The scalp of A. kooloo-kamba, taking Johanna as an example, seems almost as thinly supplied with hair as A. calvus. The arrangement of hair is the same in all. 10. Features of the Face and Skull which are characteristic of the Chimpanzee. Next to the teeth, the most characteristic features of the Gorilla are to be found in the structure of its nose. The Gorilla retains B R O C ZOOL. Soc-1899, No. XXI. 21 |
