THE " SEXQAL SEASON OF MAMMALS. 33 



tion is not necessarily coincident with the oestrus in these 

 animals. 



This opens up a wide question, which I hope to treat of in 

 a separate paper, but it is necessary to refer to it here in 

 order to point out, that the limited season for conception in 

 some monkeys is no reason for regarding their dioestrous 

 cycle as in any way different from that of other animals. 



Briefly, we may say that both ovulation and oestrus are due 

 to stimulating influences. But they are not necessarily co- 

 incident in the lower animals, and they are not necessarily 

 both induced by the same means, nor at the same time. 



In the virgin domesticated rabbit I find that ovulation 

 does not occur in consequence of oestrus alone ; while various 

 observers have shown that in the bat ovulation may occur at 

 quite a different time of year from oestrus, in some cases 

 probably as much as six months may intervene between the 

 two functions in this animal (Benecke, 1879; Eimer, 1879; 

 Fries, 1879; Beneden and Julin, 1880). 



Again, as I have already noted, there may be abnormal 

 oestrus in many animals, it may occur during gestation and be 

 independent of ovulation ; while finally, it is quite certain 

 that many animals which usually experience ovulation during 

 oestrus, sometimes fail to become pregnant at that time in 

 consequence of the failure of the function of ovulation. 



Such being the case, it may truly be said the period of 

 oestrus is not invariably identical with the period of ovula- 

 tion ; the two are separate functions, possibly closely asso- 

 ciated, but also possibly widely divergent. 



In monkeys we have an instance of animals in which the 

 rhythm of ovulation may be different from the rhythm of 

 oestrus, but it must not be supposed, on this account, that 

 either of these processes is not homologous with the same 

 process in other animals in which the rhythm may be 

 identical. It would seem as if the sexual activity of these 

 animals had been developed more than, and out of propor- 

 tion to, the ovarian activity; or, in other words, that their 

 sexual powers were greater than their powers of reproduction. 



VOL. 44, PART 1. NEW SERIES. C 



