58 AVALTRK HEAPE. 



trous Mammals in the Absence of the Male. — This 

 is shown to be affected by climatic and by individual influ- 

 ences, to be more frequent in domesticated than in wild 

 animals of the same species, and to be variously affected by 

 captivity. 



The Duration of the Sexual Season in Polyoestrous 

 Mammals in the Absence of the Male. — The sexual 

 season in these animals is affected by the duration and the 

 recurrence of the dicestrous cycle ; as in monoestrous mam- 

 mals, it is shown to be affected by climatic and individual 

 influences, by domestication and captivity. 



It is here that we are first brought into contact with monkeys 

 and man, and I have endeavoured to show that the sexual 

 season which undoubtedly exists in monkeys, exists also in 

 certain human peoples in the pi'esent day, while there is some 

 evidence that, in tlie past, all peoples were similarly affected, 

 and that a definite sexual season was the rule. The fact 

 that, in spite of the regular recurrence of the oestrus, monkeys 

 have only a limited season during which conception is possible, 

 is drawn attention to. It is pointed out that this is due to 

 the fact that the ovary is not active all the year round, 

 and evidence is brought to show that the function of ovula- 

 tion is also not necessarily coincident with oestrus in various 

 other mammals. This condition is apparently due to the 

 want of sufficient energy for both oestrus and ovulation. 



The Duration of the (Estrus in Monoestrous and 

 Polyoestrous Mammals in the Absence of the Male. — 

 Knowledge of this point is practically confined to domesti- 

 cated mammals and to certain animals in captivity, and the 

 evidence, which a study of these animals renders available, 

 shows that the duration of oestrus is very variable, not only 

 in different species, but also in different individuals of the 

 same species, and in the same individuals at different times. 



There is greater variation in this respect among monoestrous 

 than among polyoestrous mammals, as a rule. 



The Effect of Maternal Influences on the Sexual 

 Season and (Estrus. — These may or may not completely 



