SPECIAL EXPRESSIONS: CHAP. V. once did I see a very slight frown. On another occasion, I tickled the nose of a chimpanzee with a straw, and as it crumpled, up its face., slight vertical furrows appeared between the eyebrows. I have never seen a frown on the forehead of the orang. The gorilla, when enraged, is described as erecting its crest of hair, throwing down its under lip, dilating its nostrils,- and uttering terrific yells. Messrs. Savage and Wyman 19 state that the scalp can be freely moved backwards and forwards, and that when the animal is excited it is strongly contracted; but I presume that they mean by this latter expression that the scalp is low- ered; for they likewise speak of the young chimpanzee, when crying out, " as having the eyebrows strongly con- tracted." The great power of movement in the scalp of the gorilla, of many baboons and other monkeys, de- serves notice in relation to the power possessed by some few men, either through reversion or persistence, of vol- untarily moving their scalps.20 Astonishment, Terror.—A living fresh-water turtle was placed at my request in the same compartment in the Zoological Gardens with many monkeys; and they showed unbounded astonishment, as well as some fear. This was displayed by their remaining motionless, star- ing intently with widely opened eyes, their eyebrows being often moved up and down. Their faces seemed somewhat lengthened. They occasionally raised them- selves on their hind-legs to get a better view. They often retreated a few feet, and then turning their heads over one shoulder, again stared intently. It was curious to observe how much less afraid they were of the turtle than of a living snake which I had formerly placed in 10 Boston Journal of Nat. Hist. 1845-4-7, vol. v. p. 423. On the Chimpanzee, ibid. 1843--44, vol. iv. p. 365. 20 See on this subject, ' Descent of Man,' vol. i. p. 20.