PREHENSILITY OF TAIL 
THE DIANA MONKEY 
The macaques of Asia are represented in Africa by 
a kindred pair of genera of monkeys, known technically 
and respectively as Cercopithecus and Cercocebus, and in 
pseudo-vernacular, as Guenons and. Mangabeys. They 
have always long tails, which, as has been noted, the 
macaques have not always ; and the mangabeys possess 
no laryngeal pouch capable of inflation such as is to be 
found in the macaques. The Cercopitheci are apt to 
run to bright spots of colour about the nose, and their 
fur generally is more gaily coloured than in the sombre 
macaques. The Diana monkey, Cercopithecus diana, 
is as good a type as any other of this extensive genus, 
which contains more than forty species. This monkey 
like some others of its congeners is bearded, white 
bearded, and there is a good deal of bright chestnut or 
orange colour about the body. Itis like other guenons 
essentially tree dwelling and social, moving about in 
herds; like most monkeys it is affable when young, 
but morose and treacherous when older. Like all © 
others of the apes of the Old World its tail cannot grasp 
the branches which it traverses in the fashion so con- 
venient to most of the monkeys of America; and that 
there should be this distinction is one of the remark- 
able facts about monkeys. Why a prehensile - tail 
should have been developed in one half of the globe 
and not in the other in creatures which lead for all 
practical purposes identical lives, and are plainly most 
closely allied, is a mystery apparently insoluble. 
Evolution seems so to speak to have gone out of its 
way in denying this favour, which it has granted so 
widely and toso many and such varied types of animals, 
e.g. marsupials, lizards, snakes, etc., etc. Anyhow the 
long tail of the Diana monkey and its immediate allies 
is at best a balancing pole to secure a safe transit across 
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