I 



NATURAL SELECTION 



what slow in operation ; so that in a fierce 

 struggle it will often happen that its action is 

 not prompt enough to preclude a return of 

 compliments fatal to the snake. When a tiger 

 tears open the jugular vein of his enemy, the 

 enemy is placed hors de combat at once ; but 

 when the rattlesnake has bitten, there is nothing 

 to prevent the foe from employing his few 

 remaining moments in tearing the serpent to 

 pieces. Hence the rattlesnake must be pecu- 

 liarly benefited by an apparatus which serves 

 as a signal to warn enemies of his presence, and 

 to keep them from attacking him. His more 

 formidable enemies, belonging chiefly to the 

 mammalian class, are certainly intelligent enough 

 to profit by such warning and shun the danger ; 

 and as it is plainly for the snake*s advantage to 

 avoid even a conflict, it is clear that he is prac- 

 tically helped even less by his terrible bite than 

 by his power of threatening a bite. 



This explanation seems to me quite sound 

 in principle. Yet if we adopt it, there is no- 

 thing to prevent us from giving due weight also 

 to Professor Shaler*s suggestion. The success 

 with which the note of the cicada is counter- 

 feited by the rattle is a point to be more fully 

 determined by further observation. And if it 

 turns out that the rattle fulfils the double pur- 

 pose of alarming sundry animals that are hos- 

 tile and of enticing sundry others that are good 



43 



