10 WALTER HKAPE. 



season renders it necessary to discriminate clearly between 

 til em. 



The result of the foregoing- may be summarised thus : 

 when the male has not access to the female during the sexual 

 season, or when insemination at that time does not result in 

 the fertilisation of an ovum, pro-oestrum and oestrus are 

 followed by metoestrum and, if the animal be polyoestrous, 

 dioestrum is followed by another pro-oestrum, and such di- 

 oestrous cycles continue so long as the sexual season lasts; 

 whereas if the animal be monoestrous, or if the dioestrous 

 cycles of the polyoestrous animal be ended, anoestrum follows, 

 and persists until a new sexual season occurs. 



A few examples will render the foregoing somewhat more 

 clear. Among monoestrous mammals is the wolf, which, in 

 the wild state, experiences only one sexual season at a 

 particular time each year; in her case pro-oestrum and oestrus 

 are followed, when conception does not take place, by niet- 

 oestrura, and the whole of the remainder of the year is 

 occupied by anoestrum. She therefore experiences a single 

 anoestrous cycle each year. 



Another monoestrous animal is the domestic bitch ; but in 

 her case, in the absence of gestation, the anoestrous cycle 

 may recur two, three, or even four times each year. 



Among polyoestrous mammals the mare may be taken as 

 an example ; during a certain portion of the year, of variable 

 extent, she undergoes a series of dioestrous cycles when she 

 is not pregnant; this portion of the year is her sexual 

 season; when it is over anoestrum occurs and lasts until the 

 commencement of the same time the following year. 



The human female, who is also a polyoestrous mammal, 

 under certain circumstances has a continuous series of 

 dioestrous cycles throughout the year when she is not preg- 

 nant, and is thus subject to a sexual season during tlie whole 

 of her reproductive period. 



(2) When Eeproduction does take place. — In this 

 case the pro-oestrum is followed by oestrus, during which 

 period insemination occurs and the ovum or ova are fer- 



