132 THE PHYSIOLOGY OF REPRODUCTION 



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 seasonable stimuli, 

 and without even the occurrence of oestrus.^ 



There has been a considerable amount of controversy regarding 

 the periods at which ovulation occurs in the Primates, the question 

 being discussed at some length in three papers by Heape.^ This 

 author has shown that ovulation and menstruation 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 particular time of the year, although there is 

 evidence that primitive man agreed with the lower Primates in 

 having a definite sexual season (during which ovulation occurred). 

 (See p. 64.) Van Herwerden ^ 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* 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 divergence 

 of opinion in regard to the usual time for the discharge of the ova. 

 Some authors express the belief that ovulation occurs before 

 menstruation, others that it takes place during that process, and. 

 others again that it follows menstruation. Hergesell'' has lately 

 adduced evidence which, in his opinion, points to the conclusion that 

 ovulation precedes menstruation, but the occurrence of corpora lutCa 

 of uncertain age in the ovary cannot be regarded as supplying 

 definite proof. There are reasons, on the other hand, for concluding 

 that, primitively at any rate, the most usual period for ovulation in 

 the human female was during a definite cestnis following a pro- 

 cestrum, as in many of the lower Mammals ; for the period of most 

 acute sexual feeling is generally just after the close of the menstrual 



1 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 ovulation 

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

 vol. XXV. (Feb. 1907). 



2 Heape, Phil. Trans., B., vol. clxxxv., 1894, and vol. clxxxviii., 1897. 

 Trans. Obstet. Soc, vol. xL, 1898. 



8 Van Herwerden, " Bijdrage tot de Kennis van den Menstruellen Cyclus," 

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



* Pocock, "Notes upon Menstruation, etc.," Froc. Zool. Soc, 1906. 



5 Hergesell, " Das zeitliche Verhalten der Ovulation zur Menstruation," 

 Inaug. Dws., Leipzig, 1905. Cf. Nielsen, p. 107. 



