ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 253 



The male sexual or rutting season implies a period of special 

 activity of the generative organs of the male, during which he is desirous 

 of coition and normally capable of inseminating the female. Rutting 

 males, e.g. stags, have a special sexual season ; those which do not rut 

 experience sexual capability all the year round. 



tt In the case of the female the activity of her generative organs and 

 the form which that activity takes is modified by conception, and it is 

 necessary to distinguish what occurs when reproduction does not take 

 place (i.e. in absence of a male or when coition is not followed by con- 

 ception) and when reproduction does take place. When reproduction 

 does not take place, the simplest form of the female sexual season in- 

 cludes («) the pro-oestrum or pro-cestrous period ("coming in season"), 

 and (b) the oestrus or climax (" heat," " season," " brim," &c). Some- 

 times oestrus occurs without the pro-cestrum, e.g. in pregnancy ; there 

 is in this abnormal oestrus a congestion of the copulatory organs, but 

 the changes in the uterus which are evident in normal oestrus are 

 apparently absent. 



If conception does not occur during oestrus the activity of the 

 generative organs gradually subsides during a definite period (the inet- 

 cestrum), followed by a fallow or resting period (the ancestrum). The 

 lour periods pro-oestrum, oestrus, metoestrum, and anoestrum constitute 

 an "aucestrous cycle." 



A more complicated form occurs when the metoestrum is followed 

 not by an anoestrum but by a brief dioestrum, usually lasting but a few 

 days ; and Mr. Heape distinguishes monoestrous mammals, e.g. wolf 

 (which experience a single oestrus during each sexual season, or, in 

 other words, those in which the anoestrous cycle only occurs) from 

 polycestrous mammals, e.g. mare (whose sexual season is occupied by 

 a series of dioastrous cycles, or, in other words, those who experience a 

 series of recurrent oestri). 



When reproduction does take place, the pro-cestrum is followed by 

 oestrus ; during this period insemination and fertilisation occur, gestation 

 results, and persists until parturition. After parturition there may be 

 a considerable interval of rest, even beyond the limits of an anoestrous 

 period, or, on the other hand, parturition may be followed almost im- 

 mediately, and in spite of the nursing period, by pro-oestrum, oestrus, 

 insemination, and renewed gestation. In the same animal, moreover, 

 there may be recurrent gestation at one time of year, and a resting 

 period after parturition at another. The author maintains that the 

 different types of breeding phenomena conform to one plan. 



In regard to the sexual season of male mammals, Mr. Heape notices 

 a number of interesting facts. Wapiti stags have naturally a special 

 limited rutting season, but in the Gardens of the Zoological Society 

 they rut all the year round except during the casting and re-growth of 

 the antlers. The male camel in the Gardens ruts at much the same time 

 as the female camels experience oestrus in Mongolia, even when there are 

 no female camels in the Gardens. While there is no doubt that the 

 proximity of the two sexes (dog, Semnopithecus entellus, rabbit) may 

 stimulate both oestrus and rutting, the general reproductive cycle per- 

 sists apart from this. 



The pro-oestrum of female mammals is always associated with hyper- 

 trophy and congestion of both external and internal sexual organs and 



