CHANGES IN THE OVARY 137 



maturation and ovulation depend upon the temperature of the 

 early months of the year, occurring generally in February or 

 March, but sometimes as late as April. 1 Ovulation takes place 

 some days or even weeks after the formation of the first polar 

 body. It would appear, then, that in bats the follicles can 

 discharge spontaneously under the influence of appropriate 

 seasonal stimuli, and without even the occurrence of oestrus. 2 



There has been a considerable amount of controversy re- 

 garding the periods at which ovulation occurs in the Primates, 

 the question being discussed at some length in three papers by 

 Heape. 3 This author has shown that ovulation and menstrua- 

 tion are not associated in monkeys (at any rate not necessarily), 

 and that whereas, in both monkeys and the human species, 

 menstruation may occur periodically all the year round, in 

 monkeys there is a limited season for conception and ovulation ; 

 while in civilised woman this period is not limited to any par- 

 ticular time of the year, although there is evidence that primi- 

 tively man agreed with the lower Primates in having a definite 

 sexual season (during which ovulation occurred). (See p. 71.) 

 Van Herwerden 4 has adduced further evidence which shows 

 that there is no apparent connection between ovulation and 

 menstruation, either in monkeys or in the aberrant lemur, 

 Tarsius spectrum. It would seem probable, however, in view 

 of Pocock's observations 5 upon the occurrence of a pronounced 

 post-menstrual oestrus in certain monkeys in the Zoological 

 Gardens, that ovulation may take place at this period (that is, 

 at the close of menstruation). 



In the case of the human female there is still a great diver- 

 gence of opinion in regard to the usual time for the discharge 



1 Van der Stricht, " L'Atresie ovulaire," &c., Verhand d. Anat. Gesell. in 

 Bonn, 1901. " Les Mitoses de Maturation," &c., Nancy, 1906. 



2 In some Invertebrata which undergo cyclical changes it has been shown 

 that ovulation occurs only at certain intervals depending upon the general 

 condition of the organism. Thus in the females of certain Crustacea ovula- 

 tion regularly follows the moult and cannot precede it. Science (New Series), 

 vol. xxv. (Feb. 1907). 



3 Heape, Phil. Trans., ., vol. clxxxv., 1894, and vol. clxxxviii., 1897. 

 Trans. Obstet. Soc., vol. xl., 1898. 



4 Van Herwerden, " Bijdrage tot de Kennis van den Menstrnellen Cyclus," 

 Tijdschr. d. Ned. Dierk. Vereen, vol. x., 1906. 



5 Pocock, " Notes upon Menstruation," &c., 1'roc. Zool. Soc., 1906. 



