Clifton College Scientific Society. 17 



this membrane the bones of the fore part of the bod}^ are 

 singularly modified. Those of the fore-arm are very much 

 elongated, while that bone called the ulna (used along 

 with the radius to turn the hand) is either very small 

 or else absent, since, of course, a steady, and not a rotating 

 stroke is required for any continuous flight. Perhaps, 

 however, the strangest modification is found in that part 

 which corresponds to the hand of a man or a monkey. This 

 member, which becomes the paw of some quadrupeds, the 

 hoof of others, the flapper of a seal or a whale, the fin of a 

 fish, is, in the bat, developed so as to form a means of flight. 

 In the first place, all the fingers are prolonged almost indefi- 

 nitely, the middle one being of a greater length than the 

 whole body. The thumb is very short, but is provided with 

 a curved claw, by means of which the bat can drag itself 

 along the ground. The bones of the breast and its neigh- 

 bourhood are also altered so as to support the muscles of the 

 wings, this development being more apparent in the insect- 

 eating bats than in the fruit-eating species, as the former 

 have more need of swift flight. The breast bone, too, is very 

 strong, and exhibits a ridge or keel not unlike that which is 

 found in the sternum of birds. 



The hind legs and feet appear weak and little developed, 

 when compared with the fore parts of the body of which we 

 have just been speaking. There is, however, one peculiarity of 

 the feet which is certainly worthy of notice. This is a 

 peculiar development, or ' tuberosity,' as it is called, of the 

 heel bone, which forms a kind of thin bony spur, running 

 between the double membrane towards the tail. 



Having now glanced at the formation of the skeleton, we 

 will proceed to other characteristics of the family of bats 

 even more curious, namely, the development of the organs of 

 the senses. The eyes are exceedingly small in the insec- 

 tivorous species. The organs of hearing, on the contrary, are 

 very highly developed. The ears are double, consisting of 

 an inner and an outer ear, and they are not unfrequently 

 very large, being sometimes apparently qiaite out of propor- 

 tion to the rest of the body. The inner ear is very large — 

 larger relatively than in almost any other animal. Its use 

 seems to be to guard against the rush of air during flight. 

 While at rest, the outer ears are folded back, and the inner 

 alone exposed. But, besides the senses of hearing and sight, 

 bats seem almost to have an extra sense peculiar to them- 

 selves. Indeed, this was at one time considered to be the 

 case, though now, however, it is supposed to be only the 



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