CHAPTER LII 



MUSCULAR LOCOMOTION— FLYING MAMMALS, BIRDS, 



AND REPTILES 



The Bats (Chiroptera) among Mammals are expert flyers, and 

 so, of course, are the vast majority of Birds, while probably all 

 of them which do not now possess this power are descended 

 from forms which did. One long since extinct order of Reptiles 

 (Pterosauria) included a great variety of species capable of flight. 



THE FLIGHT OF BATS (Chiroptera) 



The Bats are probably an offshoot from the stock in which 

 the Insect- Eating Mammals (Insectlvora) took origin, though our 

 knowledge of their past history is far too imperfect to throw 

 any light upon the stages in the evolution of their organs of 

 flight. But the order is one of very considerable antiquity, and 

 such evidence as has been obtained proves that the oldest species 

 so far known were fully equipped with flying membranes. 



On examining a typical Bat, such as the Pipistrelle ( Vesperugo 

 pipistrelhis, fig. 829), we find a thin flying-membrane (patagium) 

 in the form of a fold of skin, extending between fore and hind 

 limb on either side. There is also a fold between the neck and 

 the front edge of the fore-limb, and a steering membrane which 

 unites the hind-limbs with one another and the tail. In some 

 bats the latter is partly free. As to their extent, the various 

 folds are very like the parachuting folds of a Colugo (see 

 p. 282), but are much thinner than in that animal. There is a 

 remarkable difference between the two cases as regards structure. 

 For the Bat's forearm is remarkable long, and bent sharply for- 

 wards on the upper-arm, and though the hook-bearing thumb is 

 relatively short, the fingers are enormously drawn out, serving as 

 supports to the main part of the flying membrane, and compar- 

 able to the ribs of an umbrella. And it may be added that both 



