44 THOSE OTHER ANIMALS. 



nearly to it in this respect, but the dog is to a great extent 

 what man has made him by careful breeding and selection ; 

 and yet even in that case the great St. Bernard is not so 

 large in proportion to the tiny toy terrier as is the giant boa 

 of tropical forests by the side of some of the slender little 

 whip snakes. Undoubtedly the snake in prehistoric times 

 grew to much larger dimensions than at present, and skeletons 

 of snakes have been found in America by the side of which 

 the largest existing python is absolutely insignificant. Indeed, 

 they rival in size the largest sea-serpent, as described by its 

 beholders. The serpent that kept a whole Roman army at 

 bay was but a pigmy to these extinct creatures, and man 

 has reason to congratulate himself that they probably dis- 

 appeared before he had any opportunity of coming into 

 contact with them. 



No theory has been offered by men of science why some 

 species of snakes should be provided with venomous fangs, 

 while others have no such advantage, and there have been 

 hot arguments whether the original father of all snakes was 

 or was not so furnished. The balance of probability would 

 certainly appear to be with those who argue that he must 

 have had venomous teeth. Had it not been so, it is difficult 

 to believe that his descendants could by any process of 

 survival or selection have established poison bags in their 

 jaws, with the necessary apparatus for passing that poison 

 through hollows in the fangs. Upon the other hand, it is 

 easy to understand that had the snakes all been originally 

 so furnished, some of them might, either from accident or 

 from incautiously grasping a round stone under the belief 

 that it was a bird's egg, have knocked out their fangs, and 

 that their descendants might have been born without them. 



