336 THE HARMONIES OF NATURE. 



both leading an arboreal life in the forests of South America, 

 are likewise provided with long prehensile tails, which afford 

 them great assistance in wandering from branch to branch. 



Among the mammals of the Old World we find the pos- 

 session of a prehensile tail confined to the phalangers, a singular 

 genus of marsupial animals, peculiar to Australia and the 

 adjacent isles. These creatures lead an indolent retired life 

 in the forests, and feed partly upon the fruits of trees, partly 

 upon the insects they manage to catch during their nocturnal 

 rambles. 



The tail, which in all these cases renders such essential ser- 

 vices in climbing, is so made as to be of great assistance to the 

 kangaroos in the performance of their enormous leaps. Extremely 

 thick and muscular at the base, and gradually tapering, they 

 rest upon it when assuming an erect or sitting posture, and its 

 powerful action when springing jerks their body into the air 

 with a force hardly inferior to that of their limbs. If the caudal 

 appendage of the American monkeys deserves the name of a 

 fifth hand, the tail of the kangaroo may thus well be called a 

 third or additional hind-leg. 



In the cetaceans the tail is of still greater importance, as here 

 it is the chief organ of locomotion. The two horizontal fins 

 which terminate the tail of the Greenland whale attain a width 

 of twenty-four feet, and cover a space of two hundred square 

 feet, and these extraordinary dimensions may serve to give an 

 idea of the extraordinary muscular power requisite to set them 

 in motion. 



Among the other mammalia leading a semi-aquatic or am- 

 phibious life, the tail is likewise a highly important locomotive 

 organ. Thus the otter, the duck-billed platypus, the beaver, 

 are indebted to their long and powerful caudal appendages for a 

 great part of their velocity in swimming; and although the 

 hind-legs of the seals chiefly impel them through the water, they 

 also derive considerable assistance from their tail. 



The long-tailed manis, a native of Africa, makes use of this 

 organ, which is more than twice as long as the body, and en- 

 tirely covered with scales, as a covering or a shield for its head, 

 neck, and back. 



The East Indian perigolin derives great assistance from the 

 tail in reconnoitring, resting upon it and its hind-legs, and 



