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Show 170 MR. R. I. POCOCK OX A HAINAN GIBBON. [May 16, St. Croix, who procured her in the island of Hainan on July lltli, 1897. She had thus been in captivity nearly six years and seven months. On the testimony of natives, her owner believed her to be about six weeks old at the time of capture; but since, as he affirms, she was already weaned and capable of fending for herself in the matter of food, it is probable that she was very much older than was supposed. On the assumption that she was at least six months old, it may be inferred that the beginning of 1897 was the approximate date of her birth. Menstruation set in at the end of the first week of December 1903 ; and taking this as the sign of maturity, coupled with the fact that she has not increased appreciably in size since her arrival in the Gardens, it may be assumed that she became ^ adult when about seven years old. And in view of the close affinity between the various species of Gibbons and the subequality in size of full-grown individuals, it may be further inferred that about seven years are required on an average for these animals to reach maturity*. Menstruation. Very little appears to be known about the menstruation of Gibbons. In Chimpanzees, according to Dr. Keith (P. Z. S. 1899, p. 297), the discharge is sanguineous in colour, profuse, monthly in occurrence, and three days in duration. In our Hainan Gibbon it is also sanguineous, stains the floor of the cage, and, according to her keeper, Mansbridge, who also looked after the Society's historic Chimpanzee " Sally," is about the same in quantity relatively to the size of the animals as in that ape. The pudendal organs are always conspicuous by reason of their turgescence, and no very conspicuous change in their condition precedes the menstrual discharge. In this particular the Gibbon differs markedly from certain Cercopithecidse (such as Baboons, Macaques, and Mangabeys), and also, to judge from published and verbal accounts, considerably, though to a lesser degree, from Chimpanzees. With the help of Mansbridge and Robertson, the two keepers of our Anthropoid Apes, I recorded the dates of the appearance of the discharge during the autumn, winter, and spring. The first noted was from Sept. 12 to 14, the second from Oct. 14 to 16, and the third from Nov. 19 to 21. During December the animal had a severe illness, beginning with an influenza cold and ending with diarrhoea, which was accompanied by extreme wasting and weakness. This illness extended over the time for menstruation, which did not appear in December. In January also there was no sign of it observable, although by the middle of that month she had apparently recovered her normal health. It is probable, I think, that the cessation for these two midwinter months was due to the illness. But it is by no means impossible that cessation during that time of the year is normal. The question can only be * Perhaps the Siamang (Symplialangus), which exceeds the other Gibbons in dimensions and differs from them in other respects, will be found to be an exception. |