36 



ANIMAL LOCOMOTION. 



and birds. The wings of the bat are deeply concave, and so resemble the 

 wings of beetles and heavy-bodied short-winged birds. The bones of the 

 arm (r), forearm (d), and Jiand {n, n, n) of the bat (fig. 17) support the 

 anterior or thick margin and the extremity of the wing, and may not inaptly 

 be compared to the nervnres in corresponding positions in the wing of 

 the beetle.— On(7i?iaZ. 



Fig. 17. — The Bat (Pliyllorhina gracilis, Peters). Here the travelling-surfaces 

 (r d e f, a n n n) are enormously increased as compared with that of the 

 land and water animals generally. Compare with figures from 10 to 14, 

 p. 34. r Arm of bat ; d forearm of bat ; ef,nnn hand of ha.t.— Original. 



Although no lizard is at present known to fly, there can 

 be little doubt that the extinct Pterodactyles (which, accord- 

 ing to Professor Huxley, are intermediate between the lizards 

 and crocodiles) were possessed of this power. The bat is 

 interesting as being the only mammal at present endowed 

 with wings sufficiently large to enable it to fly.-^ It affords 

 an extreme example of modification for a special purpose, — - 

 its attenuated body, dwarfed posterior, and greatly elongated 

 anterior extremities, with their enormous fingers and out- 

 spreading membranes, completely unfitting it for terrestrial 

 progression. It is instructive as showing that flight may be 

 attained, without the aid of hollow bones and air-sacs, by 

 purely muscular efforts, and by the mere diminution and 

 increase of a continuous membrane. 



As the flying lizard, flying lemur, and bat (figs. 15, 16, and 

 17, pp. 35 and 36), connect terrestrial progression with aerial 

 progression, so the auk, penguin (fig. 46, p. 91), and flying- 

 fish (fig. 51, p. 98), connect progression in the water with 

 progression in the air. The travelling surfaces of these ano- 

 malous creatures run the movements peculiar to the three 

 highways of nature into each other, and bridge over, as it 

 were, the gaps which naturally exist between locomotion on 

 the land, in the water, and in the air. 



1 The Vampire Bat of the Island of Bonin, according to Dr. Buckland, can 

 also swim ; and this authority was of opinion that the Pterodactyle enjoyed 

 similar advantages. — Eng. Cycl. vol. iv, p. 495. 



