THE (ESTROUS CYCLE IN THE MAMMALIA 63 



of dicestrous cycles usually at regular montlily intervals, they are 

 not necessarily capable of breeding at every heat period. Thus 

 there is evidence that in the gorilla and chimpanzee in West 

 Africa there is a special sexual season/ and Heape ^ has shown 

 that the same can be said of Semnopithecus entellus and Macacus 

 rhesus in India, but that the exact time for breeding varies in 

 the different locahties. Thus in Simla Macacics rhesus copulates 

 about October, and gives birth to young about August or 

 September in the following year, whereas on the plains around 

 Muttra it seems probable that March is the usual month when 

 young are born. However, Mr. Sanyal, the Superintendent of 

 the Zoological Gardens in Calcutta, expressed the opinion that 

 M. rhesus can breed at all times of the year. On the other hand, 

 it has been shown by van Herwerden ^ that Cercocebus in the 

 Island of Banha breeds only, as a rule, in the late summer or 

 early autumn. 



Heape * states that in the Moor macoe in the Gardens in 

 London there is definite oestrus which always occurs after the 

 cessation of the menstrual discharge, and persists for two or 

 three days, and Elhs ^ has shown that this is also probably the 

 case with the orang utan as well as with various monkeys. 



Pocock^ has given some interesting details concerning the 

 phenomena which attend the menstrual process in various 

 monkeys and baboons in the Zoological Society's Gardens. He 

 states that the females of many species at about the time of 

 menstruation exhibit extreme inflammation of the naked area 

 surrounding the genital and anal orifices. An inflammatory 

 sweUing was noticed in various species of Cercocebus, and Papio 

 and in Macacus nemestrinus^ but not in Cercopithecus, or in 



' Winwood Keade, Savage Africa, London. Mohrike, Das Ausland, 

 1872. Garner, Gorillas and Chimpanzees, 1896. 



^ Heape, " The Menstruation of Semnopithecus entellus," SMI. Trans. B., vol. 

 olxxxv., 1894. " The Menstruation and Ovulation of Macacus rhesus." Phil, 

 Tram. B., vol. clxxxviii., 1897. 



' Van Herwerden, loc. cit. * Heape, "The Sexual Season,'' &c. 



' Havelock Ellis, Psychology of Sex, vol. ii., Philadelphia, 1900. 



° Pocock, " Notes upon Menstruation, Gestation, and Parturition of some 

 Monkeys that have lived in the Society's Gardens," Proc. Zool. Sac, 1906. 



' Similar observations had been previously described in Cercopithecus, 

 Papio, and other species by certain of the older naturalists. See St. Hilaire 

 and Cuvier, SiHt. Nat. des Mammifires, 1819-35. 



