62 THE PHYSIOLOGY OF REPRODUCTION 



ovulation. It has been shown by Benecke, 1 Eimer, 2 van 

 Beneden, 3 and Salvi, that whereas copulation may occur in the 

 autumn, the ova are not fertilised until after the winter 

 hibernation, the spermatozoa in the meantime lying dormant. 

 Salvi, 4 however, describes the bats in the Grotta dell' Inferno, 

 near Sassari, as copulating also in the spring, but it is suggested 

 that coition at this season may only take place among those 

 females which have failed to become inseminated effectively in 

 the previous autumn. 5 It does not appear to be known whether 

 the polycestrous condition ever occurs in bats. 



It is stated that a " menstrual " (procestrous) flow has been 

 observed in the flying fox (Pteropus). 6 



PRIMATES 



Lemurs. Among Lemuroids, Stratz 7 has shown that in 

 Tarsius spectrum there is a sanguineous prooestrous discharge 

 almost as concentrated as in monkeys. This is presumably 

 followed by an cestrous period. It is stated also that Tarsius 

 experiences an uninterrupted series of dioestrous cycles (i.e. a 

 condition of continuous polycestrum) ; but that, whereas con- 

 ception is possible at any time of the year, breeding occurs 

 more frequently in October and November than at other seasons. 8 



Monkeys. The essential similarity between the procestrum in 

 the lower Mammalia and menstruation in monkeys will be made 

 clear in the next chapter, when the histological changes which 

 occur in the uterus are described. The consideration of the sub- 

 ject, however, is somewhat complicated by the fact pointed out 

 by Heape 9 that, whereas monkeys may have a continuous series 



1 Benecke, " Ueber Reifung und Befruchtung des Eies bei den Fleder- 

 maiisen." Zool. Anz., vol. ii., 1879. 



2 Eimer, "Ueber die Fortpflanzung der Fledermaiise," Zool. Anz., vol. ii. 

 1879. 



3 Van Beneden, " Observations sur la Maturation, la Fecondation, et la 

 Segmentation de 1'oeuf chez les Cheiropteres, Arch, de Biol., vol. i., 1880. 



4 Salvi, " Osservazioni sopra 1'Accoppiamento dei Chirotteri nostrani," 

 Atti della Societd Toscana di Scienze Naiurali. vol. xii., 1901. 



5 Duval, " Etudes sur 1'Embryologie des Cheiropteres," Premiere Partie, 

 Paris 1899. 



6 Wiltshire, loc. cit. 1 Stratz, loc. cit. 

 8 Van Herwerden, loc. cit. 9 Heape, loc. cit. 



