HI LECTURES ON EVOLUTION 113 



There are four fingers. These four fingers are 

 large, and three of them, those which answer to 

 the thumb and two following lingers in my hand 

 are terminated by claws, while the fourth is 

 enormously prolonged and converted into a great 

 jointed style. You see at once, from what I have 

 stated about a bird's wing, that there could be 

 nothing less like a bird's wing than this is. It 

 was concluded by general reasoning that this finger 

 had the office of supporting a web which extended 

 between it and the body. An existing specimen 

 proves that such was really the case, and that 

 the pterodactyles were devoid of feathers, but 

 that the fingers supported a vast web like that 

 of a bat's wing ; in fact, there can be no doubt that 

 this ancient reptile flew after the fashion of a bat. 



Thus, though the pterodactyle is a reptile which 

 has become modified in such a manner as to enable 

 it to fly, and therefore, as might be expected, pre- 

 sents some points of resemblance to other animals 

 which fly ; it has, so to speak, gone off the line 

 which leads directly from reptiles to birds, and has 

 become disqualified for the changes which lead to 

 the characteristic organisation of the latter class. 

 Therefore, viewed in relation to the classes of 

 reptiles and birds, the pterodactyles appear to me 

 to be, in a limited sense, intercalary forms ; but 

 they are not even approximately linear, in the 

 sense of exemplifying those modifications of 

 structure through which the passage from the 

 reptile to the bird took place. 



VOL. IV I 



