98 APES AND MONKEYS 



they are not in need of shelter. Of course birds and 

 other oviparous animals build nests, as they do elsewhere. 

 The period of incubation makes this necessary. 



The longevity of these apes is largely a matter of con- 

 jecture, but from a cursory stud}' of their dentition and 

 other facts of their development, it appears that the male 

 reaches the adult stage at an age ranging from eight to 

 ten years, while the' female matures between six and eight. 

 These appear to be the periods at which they pass from 

 the state of adolescence. Some of them live to be per- 

 haps forty years of age, or upwards, but the average life 

 is probably not more than twenty-one to twenty-three years. 

 The average of life is, doubtless, more uniform with them 

 than with man. These figures are not mere guesswork, 

 but are deduced from reliable data. 



The period of gestation in both these apes is a matter 

 that cannot be stated with certainty. Some of the natives 

 say that it is nine months, while others believe that it is 

 seven months or less. There are some facts to support 

 each of these claims, but nothing is quite conclusive. The 

 sum of the evidence that I could find rather points to a 

 term of four and a half months, or thereabouts, as the true 

 period. During the months of January and February the 

 male gorillas are vociferous in their screaming, the young 

 adults separate from the families, and other things indicate 

 that this is the season of pairing and breeding. They 

 may not be strictly confined to this period, but the infer- 

 ence that they are so is well founded. It is quite certain 

 that the season of bearing the young is from the beginning 

 of May to the end of June. It is about this time that the dry 



