THE "sexual season" OF MAMMALS. 41 



In certain bloodhounds a well-known breeder (Mr. Brough) 

 has observed oestrus to last twenty-one days, but only very ex- 

 ceptionally, and not as a characteristic of an}^ particular bitch. 



There can be little doubt the persistence of oestrus in 

 bitches may be influenced by their temperament, by their 

 food, and by the particular conditions of existence expe- 

 rienced by each bitch. 



Wolves, jackals, and foxes in the Zoological Gardens have 

 about the same duration for oestrus as the average bitch, 

 from seven to nine days. In the cat CBstrus lasts nine to ten 

 days (Hamilton, 1896); in tigers in captivity (Zoo.) for 

 eight days at the longest. In bears, on the other hand (Zoo.), 

 oestrus appears to last continuously for two to three months ; 

 it must be recollected, however, that this occurs with females 

 kept together with males under conditions which, while they 

 may very probably excite sexual feelings, do not result in 

 gestation. 



Among wild animals the duration of the oestrus can only 

 be assumed by comparison with other individuals of the 

 same species in captivity ; although the duration of the 

 sexual season may be inferred from the known season during 

 which parturition takes place, the duration of the oestrus 

 cannot be so determined. 



Among polyoestrous mammals there is not such great varia- 

 tion in the duration of oestrus, since, instead of a long period 

 of oestrus, these animals exhibit a recurrence thereof; still 

 there is some difference apparent : the domestic sheep has 

 oestrus for only a few hours, say twelve hours ; the cow for 

 not more than twenty-four hours as a rule; while antelope, 

 deer, and wild cattle in captivity (Zoo.) closely imitate 

 domestic cattle and sheep in this respect. 



The mare endures oestrus probably for a slightly longer 

 period as a rule, but this depends very much on the tempera- 

 ment of the individual mare, and tiie coiiditions under which 

 she is kept. 



The elephant in the Zoological Gardens has persistent 

 CEstrus for probably three to four days. 



