14 INTRODUCTION 



vespertilionid bats — statements to the contrary notwithstand- 

 ing — walk well, the sequence of their movements being that 

 typical of quadrupedal locomotion. The Horseshoes alone 

 are unable to make even a pretence of walking, and when 

 on a flat surface, lie prone and helpless, their feebleness in this 

 respect, since forearm, leg and foot are all well developed, being 

 probably due to interference with the action of the forearm 

 by their well-developed antebrachial membrane.^ In spite 

 of this, they readily climb backwards, by means of their 

 feet and thumbs, up an incline, no matter how steep, and 

 have no difficulty in taking wing from a flat surface, springing 

 with surprising agility into the air, even from narrow or cramped 

 surroundings. But, although no healthy British bat usually finds 

 any difficulty in taking flight from a flat surface, it is possible that 

 some individuals, perhaps after a heavy meal, may at times lack 

 the necessary vigour ; and all require lateral space for a forward 

 jump and expansion of the wings. In climbing, the free tip of 

 the tail is, in the vespertilionid bats, used as a kind of extra 

 limb, and with it the inequalities of a rough surface are sought 

 and held. In traversing the wires of a cage, the extended tail 

 acts as a support like the stiffened rectrices of a woodpecker or 

 tree-creeper, and even in horizontal progression it assists in 

 throwing forward the body, being brought into contact with the 

 ground on either side alternately in correspondence with the 

 action of the feet. There is no evidence that the feet are ever 

 used to aid in catching or holding the prey, but their vari- 

 able proportions in the different species, from relatively largest 

 in the W^ter Bat and Noctule to particularly small in the 

 Barbastelle, must have some meaning, and need explanation. 

 The thumbs might easily be used for holding or securing food, 

 as they are in the fruit bats and in a berry-eating bat of 

 Jamaica,^ but I know of no evidence on this point, except in the 

 case of a captive Natterer's Bat. 



Dentition : — Young bats, except the Rhino lop hid(£, are born 

 with a complete milk-dentition, the function of which is to enable 

 them to hold on to their mothers' nipples. These teeth differ 



1 As in other bats which walk poorly ; see Dobson, Catalogue of Chiroptera, 466. 



2 Phyllonycteris sezekorin of Grundlach and Peters, as observed by Osburn, op. cit. 

 infra, p. 22. 



