170 MR. E. I. POCOCK ON A HAINAN GIBBON. [May 16, 



St. Croix, who procured her in the island of Hainan on July 11th, 

 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 ai'rival 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 thi'ee days in diu^ation. 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 aj)e. 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 jaarticular the Gibbon differs 

 markedly fi-om certain Cercopithecidse (such as Baboons, Macaques, 

 and Mangabeys), and also, to judge fi-om 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 Ajaes, 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 

 diarrhea, which was accompanied by extreme wasting and weak- 

 ness. 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. Tlie question can only be 



* Perhaps the Siamaiig {Si/mp7talanffus), which exceeds the other Gibbons in 

 dimensions and differs from them in otlier respects, will be found to be an exception. 



