1^10 THE DESCENT OP liAif. 



lie was himself at first perplexed by the above action, and 

 was thus led carefully to observe several individuals of 

 various other species of monkeys, which he has long kept 

 in his house. He finds that not only the mandrill (Cyno- 

 ceplialus mormon) but the drill (C. leucophmus) and three 

 other kinds of baboons [C.hamadryas sphinx 'dndbabo2ii?i)y 

 also Cynopitliecus niger, and Macacus rhesus and 7iemes- 

 trinus, turn this part of their bodies, which in all these 

 species is more or less brightly colored, to him when they 

 are pleased, and to other persons as a sort of greeting. He 

 took pains to cure a Macacus 7'hesus, which he had kept 

 for five years, of this indecorous habit, and at last suc- 

 ceeded. These monkeys are particularly apt to act in this 

 manner, grinning at the same time, when first introduced 

 to a new monkey, but often also to their old monkey 

 friends; and after this mutual display they begin to play 

 together. The young mandrill ceased spontaneously after 

 a time to act in this manner toward his master, Von 

 Fischer, but continued to do so toward persons who were 

 strangers and to new monkeys. A young Cynopithecus 

 niger never acted, excepting on one occasion, in this way 

 toward his master, but frequently toward strangers, 

 and continues to do so up to the present time. From 

 these facts Von Fischer concludes that the monkeys 

 which behaved in this manner before a looking-ghiss 

 (viz., the mandrill, drill, Cynopithecus niger ^ Maca- 

 cus rhesus and neinestrinus) acted as if their refiec- 

 tion were a new acquaintance. The mandrill and drill, 

 which have their hinder ends especially ornamented, 

 display it even while quite young, more frequently and 

 more ostentatiously than do the other kinds. Next in 

 order comes Cynocephalus hamadryas, while the other 

 species act in this manner seldomer. The individuals, 

 however, of the same species vary in this respect, and some 

 which were very shy never displayed their hinder ends. It 

 deserves especial attention that Von Fischer has never 

 seen any species purposely exhibit the hinder part of its 

 body, if not at all colored. This remark applies to many 

 individuals of Macacus cynomolgus and Cercocebus radi- 

 atus (which is closely allied to M. rhesus), to three species 

 of Cercopithecus and several American monkeys. The 

 habit of turning the hinder ends as a greeting to an old 

 friend or new acquaintance, which seems to us so odd, is 



