THE " SEXUAL SEASON OF MAMMALS. 



1 



cycles," and by " anoestrum " in monoestrous mamma s 

 always, and in polyoestrous mammals at the close of the 

 sexual season. 



The difference between the dioestrous or ancestrous cycles 

 in the absence of the male, and the ''maternal generative 

 cycle " when oestrus is followed by insemination, fertilisation 

 of the ovum, and gestation, is drawn attention to. 



The occurrence of abnormal oestrus is noted. 



The Breeding Season of Mammals is merely touched 

 upon ; inasmuch as it concerns what happens during both the 

 sexual season and the gestation period jointly, its full con- 

 sideration is not possible in this paper. 



The Sexual Season of Male Mammals. — Males are 

 divided into two classes, those which have a special sexual 

 season, " rut," and those which are sexually capable all the 

 year round. The influence of captivity is touched upon, and 

 it is shown that, while sexual activity is not so violent in 

 captive animals as in those in the wild state, it may be 

 much more frequently or continuously exhibited. 



The Sexual Season of Female Mammals. — This is 

 considered in wild mammals in a state of nature, in those 

 which are captive, and in domestic mammals ; and the effects 

 of climatic, individual, and maternal influences are drawn 

 attention to. 



Among monoestrous mammals the effect of these influences 

 may be to increase or decrease the periodicity or the duration 

 of the sexual season, while among polyoo ' • ;• nammals the 

 effect may be to increase or decrease the uumoer of dioestrous 

 cycles in each sexual season or the duration of each cycle; 

 the effect in both classes of animals being to increase or 

 decrease their reproductive power. 



It is pointed out that the knowledge at present available 

 throws no light on the origin of the sexual season ; but that 

 it is due to a stimulus which appears to be gradually collected, 

 that it is associated with nutrition, and is manifested by excep- 

 tional vigour and bodily " condition " seems assured. 



The Periodicity of the Sexual Season in Monoes- 



