DURATION OF YOUTH IN MAMMALS 39 



fine male which has been there for seven years. Chimpanzees are 

 obtained in much larger numbers and, although they are very delicate, 

 individuals have frequently lived in captivity for a number of years. 

 The " record " is held by the London Society, and in the Gardens at 

 Regent's Park there is a chimpanzee which has lived for fourteen 

 years. Unfortunately it is a dwarf, either congenitally or as the 

 result of the artificial conditions in which it has lived. Individual 

 gibbons have lived for several years, but in most cases they too 

 succumb very quickly. 



I do not know if anthropoid apes would be likely to breed in 

 captivity, but as most of them are taken when they are very young 

 and do not live to maturity, there has been no opportunity, and I 

 do not know of any case of a birth having taken place in menageries. 

 Unfortunately, also, it is certain that little reliance can be placed 

 on the rate of growth of the apes in captivity. Better accommo- 

 dation, less coddling and more reasonable food are certainly im- 

 proving the general health of captive apes, and probably their rate 

 of growth is often more natural than it used to be. But we have 

 still to rely chiefly on comparisons with human beings, based on size, 

 the appearance of puberty, the closing of the skull bones, changes 

 in the teeth and so forth, and there is no reason to be certain that 

 such comparisons are not misleading. It is generally assumed, 

 however, that the duration of youth in anthropoid apes is from 

 eight to twelve years, and the estimate is probably not very far 

 wrong. 



The lower monkeys range in size from the large baboons, which 

 exceed gibbons in bulk and weight, to tiny monkeys like marmosets 

 which may be no larger than a small squirrel. Although on the whole 

 they are also rather delicate in captivity, so many have been kept 

 by private persons or in public institutions that it is not surprising 

 that there have been frequent successes. Many different species 

 have been bred in captivity and reared to maturity. The larger 

 monkeys, like baboons and mandrills, take from eight to twelve 

 years to grow up. Middle-sized monkeys, like common Asiatic 

 macaques, take from three to five or six years. A pair of Japanese 

 apes in the London Zoological Gardens were the parents of a baby 

 born in January 1906 ; in the beginning of 1912 the young one was 

 nearly, but not quite, fully grown. It lived with its parents in an 

 enclosure consisting of an open-air cage about ten feet by ten in 

 area, provided with branches on which to climb, and with an un- 

 heated, covered sleeping-den. Although the conditions were better 



