230 BAROX NOPCSA ON THE [Feb. 19, 



wing-fingei", could always suspend tliemselves by the remaining 

 free digits. This is, perhaps, also the reason why, in both groups, 

 ulna and radius, tibia and fibula have been reduced in a different 

 mannei'. In Birds the same problem has been solved in quite 

 another manner (musculus ambiens and peculiarities in the 

 structui-e of the tendon-sheath of muse, flexor, digit, in the 

 phalanges). Text-fig. 78 shows the hind limb of a Bat identified 

 by Dr. K. Andersen as Hipposiderus gigas. 



Text-fiff. 78. 



Hind limb of Hipposiderws. 



Since all flying animals must needs have developed from agile 

 quick-moving animals, since all living patagium-flying animals 

 (such as BracG rolans, and the other living animals mentioned 

 in this paper) are arboreal, leaping, quadrupedal creatures, and 

 since, further, a bipedal cursorial animal, on account of mechanical 

 impossibilities, can never develop a patagium — for such an organ 

 would in bipedal (i. e., erect) locomotion only catch the air and so 

 prevent running without raising the body, — and since the union 

 of fore and hind limbs is directly opposed to bipedal cursorial 

 locomotion, we can safely state that all patagium-flying a,nimals 

 originated from quadrupedal, leaping, arboreal forms. ^ 



Bats and Pterosaurs, though they support the wing in different 

 ways, still show an analogous direction of evolution — as shown by 

 the development of a patagium with all that this implies ; thus we 

 may safely state that Bats and Pterosaurs have arisen in similar 

 manner from quadrupedal arboreal forons. 



