464 



THE GENERAL PRINCIPLES OF ZOOLOGY 



Some of the most interesting facts in favor of the Darwinian 

 theory are afforded by such phenomena as protective resem- 

 blance and mimicry. By protective resemblance is commonly 



understood any resem- 

 blance between an animal 

 and its surroundings which 

 tends to protect it from its 

 enemies. Many pelagic 

 aquatic animals are so 

 perfectly transparent and 

 colorless as to be well-nigh 

 indistinguishable from the 

 surrounding water. Many 

 marine animals resemble 

 seaweed in form and color; 

 a notable example is a 

 species of sea horse, which 

 has curiously shaped 

 filamentous outgrowths on 

 the bod_\', giving it a very 

 ragged appearance ( 1 

 420). Many tropical ani- 

 mals arc striped or spotted, 

 and so resemble the 

 shadows cast by the sur- 

 rounding foliage as the 

 sunlight streams through 

 it. The insects furnish 

 many striking examples 

 of this protective resem- 

 blance ( Fig. 421); the 

 walking stick (Fig. 422) 

 and the leaf insect ( 1 

 423 ) are very like tv. 

 and green leaves respec- 

 tively; the dead-leal 

 butterfly, Kallima paralecta, of the East Indies, presents the 

 most perfect resemblance to a dead leaf, when it alights and 

 folds its wings; another butterfly of the genus Siderotic is very 



FKJ.422. Diapheromera femorata, $, the common 

 walking stick of the United States; natural size. 

 1 1 )rawn from specimen. ) 



