lo INTRODUCTION 



A third and smaller extension of the flying integument, the 

 antebrachial membrane, is stretched in front of the humerus and 

 the forearm. The wing itself may be divided, for purposes of 

 description, into two parts, viz., the lateral membrane, lying 

 between the leg and fifth digit, and the dactylopatagium, or part 

 directly borne by the fingers. 



A comparative study of the wing in young and old bats 

 of both sexes, as well as in the various species and genera, 

 is necessary. Bats are born with a high development of the 

 organs of attachment, the hind claws and thumbs, but the 

 wings, which make their appearance late in the development 

 of the embryo, are still quite small at birth, and, even when the 

 young begin to fly, differ in their proportions from those of the 

 adult (Plate II., Fig. 2, p. 16). Immaturity may, however, always 

 be recognised by the imperfectly ossified joints of the digits, 

 which when fully adult appear as definite knobs or swellings 

 traversed only by a single indefinite line (Plate I.). In imma- 

 ture specimens, on the other hand, the imperfect ossification is 

 shown by the presence of one or two small bones, the epiphyses, 

 which lie between the two joint-heads and give the appearance 

 of at least two distinct transverse lines between them. The 

 process of ossification is evidently of variable duration. I 

 have inspected a young Whiskered Bat and Pipistrelle, with 

 the phalanges fully developed as regards their length, though 

 not as regards their joints, on 26th July and 9th August 

 respectively ; but the process of fusing the epiphyses had 

 not been completed in some Lesser Horseshoes examined by 

 Mr T. A. Coward in January, nor in another specimen of the 

 same species, which came under my own notice in the March 

 following. 



Amongst adults of British bats, the females are usually the 

 larger,^ but, after deducting all differences due to age and sex, 

 there still remains a considerable amount of variation in size 

 and proportions, the cause of which is not understood. It is 

 not, however, sufficient to lessen the importance of the wing as a 

 feature of high diagnostic value. 



The actual dimensions of the various species are shown 



' This is not a universal characteristic of the CJiiroptera^ since in some fruit-eating 

 bats the male is the larger sex. 



