MAMMALS 



59 



tend in the individual to produce an inflamed condition of 

 the skin and its blood-vessels, and if inherited would explain 

 this peculiar feature of the animal. If this were the case 

 we could understand more completely why the colour of the 

 skin increases under excitement, fades during sickness, and 

 disappears after death, for a physiological association would 

 have been set up between the sexual excitement of the 

 animal and the results produced by friction. 



One other unisexual character in the mandrill is men- 

 tioned by Cuvier : it occurs in the female. Menstruation, 

 which takes place regularly once a month, is accompanied 

 by a swelling of the parts round the anus, forming a pro- 

 tuberance which is red and inflamed in appearance, and is 

 as big as the head of a child. This may well be due to the 

 accumulated effect of the violence and frequency of copula- 

 tion. 



More definite information on the indecent gesture of the 

 mandrill, which is performed also by certain other species, is 

 given in a communication published by Darwin in Nature in 

 1876, and printed as a supplemental note to the second edition 

 of his Descent of Man, 19th thousand, 1885. Joh. von Fischer 

 of Gotha observed that a young male mandrill in his 

 possession, when he first saw his reflection in a mirror, after 

 contemplating it for some time turned round and presented 

 his red hinder end to it. He subsequently ascertained that 

 not only the mandrill, but the drill, C. leucophalus, and 

 three other kinds of baboon, C. hamadryas, sphinx, and 

 babouin, as well as Cynopithecus niger, Macacus rhesus, and 

 Macacus nemestrinus, turned this part of their bodies, which 

 in all these species is more or less brightly coloured, to him 

 when they were pleased, and to other persons as a sort of 

 greeting. Von Fischer concludes that the animals acted as 

 though their reflection in the mirror were a new acquaintance, 

 that is to say, were another individual of their own species. 



