iv CONNECTING LINKS 49 



from slightly over ioo° F. to 1 12°. This highest figure 

 is attained by some Passerine birds : Hawks and their 

 allies arc never much above 109 , and Gulls rise only a 

 little above 104 . Whether these recorded temperatures 

 arc in every case quite exact may be doubted. When 

 the subject is a wild animal, the use of a clinical 

 thermometer is difficult. In the case of the python the 

 results arc quite dependable, though the thermometer, 

 laid between the folds, no doubt registered a lower 

 temperature than it would have in the mouth. With 

 other animals fresh experiments are needed. But 

 even as it is we may be quite certain that the figures 

 given are nearly right, though there may be an error 

 of a half or even a whole degree. The conclusions 

 we arrive at, then, are — (1) that there is no hard and 

 fast line to be drawn between warm and cold-blooded 

 animals, and, consequently, our warm-blooded birds 

 may be related to our cold-blooded reptiles ; (2) that 

 pterodactyls, in respect of their temperature, were 

 birdlike rather than reptilian. Before leaving this 

 subject, an objection raised by Sir Richard Owen 

 must be met. He maintained that pterodactyls must 

 have been cold-blooded since they had no feathers to 

 prevent the escape of heat from their bodies. But 

 the temperature of the body has comparatively little 

 to do with external coverings, and depends mainly 

 upon its power of generating heat and upon the 

 regulating apparatus by which it adapts itself to 

 changing conditions. 



We will now go on to other points which prove the re- 

 lationship of pterodactyls to birds, or prove, at any rate, 

 that they have developed separately on very similar lines 



E 



