624 



MONKEYS 



XXIV. 2 



and fruit, but many monkeys are specialized fruit-eaters, and the 

 molar teeth are quadrangular, with the four cusps united to make two 

 transverse ridges used for grinding, somewhat as in ungulates. These 

 specialized molars make it unlikely that the modern cercopithecids 

 could have been ancestral to the apes or man. The colon usually has 

 a sigmoid flexure and a small caecum and appendix. The reproduction 

 is similar to that of apes and man; there is menstrual bleeding and 

 haemochorial placenta. The ano-genital region (sexual skin) of the 

 female may show marked signals (swelling and coloration) at the time 



A BCD 



Fig. 400. Coloration types of various sub-species of Colobus polykomos. a. C.p. 

 vellerosus Graff, b. C.p. caudatus Thomas, c. C.p. abyssinicus Oken. D. C.p. 

 angolensis Sclater. (After P. Rodt.) 



of ovulation. The male shows continuous spermatogenesis, without a 

 breeding season. In some species there are, however, seasonal fluctua- 

 tions in the number of births. 



The cerebral cortex is always large and fissured and its frontal 

 regions well developed. Behaviour is exploratory and manipulative 

 and learning powers high. Social behaviour is elaborate and often 

 based upon polygamous families. The coat colour is often ornate (Fig. 

 400) and there are elaborate communication systems by the facial 

 musculature and vocal apparatus. 



The Cercopithecoidea include a number of variant types, many 

 common and well known. Macaca, the rhesus monkey (Fig. 401), 

 has many species in Asia and North Africa, one reaching Gibraltar. 

 Cercopithecus, the guenons, are similar animals in Africa, many highly 

 coloured. The baboons, Papio (Fig. 402), of Africa and related forms 

 in Arabia, and mandrills, Mandrillus (Fig. 403) of West Africa have 

 become secondarily terrestrial and quadrupedal and the face has 

 become elongated ('dog-face'), allowing for a long tooth-row of grind- 

 ing molars. The Colobinae are fully arboreal, leaf-eating monkeys, 

 without cheek pouches but with the stomach sacculated ; the guerezas 



