NATURE IN MOTION. 71 



creeps on shore, but actually climbs up tall fan-palms, in 

 pursuit of certain shell-fish, which form its favorite food. 

 Covered with viscid slime, he glides smoothly over the 

 rough bark ; spines^ which he may sheathe and unfold at 

 will, serve him like hands to hang by, and with the aid 

 of side fins and a powerful tail he pushes himself upward, 

 thus completing the strange picture of fish and shell-fish 

 dwelling high on lofty trees. 



In remarkable contrast with this amazing mobility of 

 fishes stands the comparative quiet of Amphibia, which, 

 double-dealing creatures as they are, now claim the dry 

 land as their home, and now the deep waters. The cun- 

 ning lizard, the creeping snake, the venomous toad, or the 

 voracious crocodile, in fine, all the disgusting animals of 

 this class, whom man looks upon with awe or horror, are 

 fortunately bound to the glebe on which they are born, 

 .and of them, as of reptiles, few, if any, love to travel. 

 The violet crab of the West Indies and South America 

 is almost the only one among them all that undertakes 

 long journeys. They live on firm land only, far from the 

 ocean, hid in dark caves or caverns of the mountains. 

 But once in the year, in April or May, the sun, the heat 

 and love penetrate the thick armor of these cold-blooded, 

 beings. All of a sudden they burst forth, from cleft and 

 crevice, and move in crowds of hundreds and thousands, 

 so that the ground, the roads and woods are covered with 

 their uncouth 'shapes. The vast army travels in strict 

 battle array ; first come strong men, then the females, in 

 closely packed columns, fifty to sixty yards wide, and often 

 half an hour long. They prefer moving at night, and the 



