122 VESPERTILIONID^— PIPISTRELLUS 



developed." If the facts as reported by Mr Whitaker be 

 correct, and assuming that the true period of gestation could 

 not have exceeded some forty-nine days, we are left with 

 the alternative explanations that either the date of ovula- 

 tion was delayed by captivity, or that either fertilisation 

 or pairing had taken place after the date of capture. The 

 case is full of interest, but does not afford much ground 

 for speculation as to its meaning. It may, however, be 

 expected that the breeding habits of a bat having such 

 slender inclinations to hibernate, must present many features of 

 interest, and will probably be found to vary with the climatic 

 conditions of different parts of its range, as in fact we know to 

 be the case in regard to the number of young. 



On the latter point, continental authorities from Pliny — 

 '* Geminos volitat amplexa infantes " ^—downwards unite in con- 

 sidering two at a birth quite usual. This is certainly not the case 

 in Britain, where the observations of Tomes, George Daniell, Mr 

 Whitaker, and others show that, as with the Noctule, one is the 

 almost invariable rule. Of five female Pipistrelles received by 

 Daniell" in July 1833, each contained a single foetus ; and Tomes 

 also was convinced by the examination not merely of British 

 specimens, but of a great number of foreign ones, that the pro- 

 duction at a birth of more than one young one is exceptional. 

 The only (and that an extremely doubtful) British reference 

 to the birth of twins which I have been able to find is 

 the merely incidental statement of Couch, that a friend 

 "observed of one to which the young ones were attached, that 

 they were separated from the teats with difficulty, and that 

 when separated they were not able to lay hold of them ; and 

 the old one then seemed quite indifferent to her young, running 

 over them without care." The act of parturition was observed 

 in one case only by Mr Whitaker. The mother clung head 

 downwards to the side of the cage and received her offspring 

 in her right wing, which she held partially extended for the 

 purpose. 



The young ones born in Mr Whitaker's cages were at 

 first stowed away under their mother's wings, exactly like 



^ Loc. cit. supra, p. 115, "[The mother] flies embracing twin young." 

 2 Proc. Zool. Soc. (London), nth Nov. 1834, 129-132. 



