34 INTRODUCTION 



The authors think that these must have spent the winter in some 

 cold or windy situation, thus rendering spring revival sluggish. 

 At all events, the female gatherings increase in size all April. 



By 5th June many wild young had made their appearance, 

 and their growth was very rapid. 



The authors ascertained that the female does not pair 

 until her second autumn, when about seventeen months old. 

 Sometimes even, although to all appearance sexually mature, 

 she remains virgin throughout the following summer, appar- 

 ently until her third autumn. There are thus in the autumn 

 assemblages three types of female. That of the first year, 

 being virgin, may be distinguished by the small and undeveloped 

 mammary and generative organs, the latter never containing 

 spermatozoa, and by the usual external indications of imma- 

 turity especially in colour, teeth, and wings. That of the 

 second year, now breeding for the first time, is more developed, 

 but the uterus is always smaller than in the adult which has 

 borne young. The latter has the mammae plainly visible, and 

 the right horn of the uterus distinctly larger than the left. 



When the bats leave their winter quarters, the virgin female 

 of the first year accompanies the adult of the same sex, but leaves 

 soon after the birth of the young. That of the second year, on 

 the other hand, even when herself virgin, never leaves the 

 company of the breeding females. The existence of the class 

 of virgin females, both of the first and of the second years, 

 throughout the spring, although it led Carl Vogt ^ to suppose 

 the necessity for spring copulation, convinced the authors that 

 no such act takes place at this season. 



That there should be no spring copulation is difficult to 

 understand, since the adult male is in train to breed from 

 September until April. The state of the organs indicates a 

 season of rut, and the authors express astonishment that, in 

 spite of this, they are so long inactive. They suggest that 

 reabsorption of the spermatozoa may take place in accordance 

 with the Brown- S^quard theory of internal secretion. Although 

 the authors express no doubt as to the absence of spring copu- 

 lation, the conclusion, in view of the condition of the male, is so 

 surprising as to seem in need of corroboration. 



' op. cit. supra, p. 32. 



