274 THE HARMONIES OF NATURE. 



but these are well formed for burrowing, and, with the addi- 

 tional assistance of their flat wedgelike snout, enable them at 

 the approach of an enemy to disappear under the sand almost 

 as quickly as the mole burrows in the ground, or the seal 

 dives under the water. 



During the summer months, the tree-frog lives chiefly on 

 the upper parts of trees, where it wanders among the foliage in 

 quest of insects, which it catches with extreme celerity, either 

 stealing softly towards its prey, or springing upon it with a 

 sudden leap. For this arboreal life it is well fitted by the 

 peculiar formation of its toes, all of which are terminated 

 by round, flat and dilated tips, whose under-surface being 

 soft and glutinous, allows it to climb with perfect security 

 and ease ; it can also adhere to any substance by its abdomen 

 (which is covered with small glandular granules), by merely 

 pressing itself against it. It is often seen suspending itself by 

 its feet to the under parts of the leaves to enjoy their shade, 

 while its green colour harmonising with that of the foliage 

 masks its presence from its prey, and enables it to escape the 

 notice of its enemies. 



Thus, however different in form or structure, the locomotive 

 organs of the reptiles constantly agree with their mode of life, 

 and a further examination of the passive or active defences of 

 these animals shows us that everywhere the want of some 

 faculty is compensated by the possession of another. 



The large American iguana, for instance, when overtaken by 

 one of its arch-enemies, the various species of the formidable 

 cat tribe, makes use of its long and powerful tail as a most 

 effective weapon of defence, lashing about with it to the right 

 and left in such a manner as to make even the jaguar pause in his 

 attack. When the* monitor-lizard is pursued by the huntsman, 

 it runs as fast as it can to its burrow; but when intercepted 

 in its flight, it defends itself courageously. Its sharp teeth 

 are able to bite through a strong boot, and its powerful tail 

 sends the dog whom it hits howling from the field of battle, 

 or lays him prostrate in the dust. Besides the activity of 

 their movements, which enables them to dart suddenly from 

 their place of concealment upon the beetles flies or gnats on 

 which they principally feed, the insectivorous lizards are 

 furnished with an extensible tongue, fissured at the extremity, 



