200 MARVELS OF THE ANIMAL WORLD 



that the hoop-snake progresses along the ground by 

 seizing its tail in its mouth and then bowling along 

 in the manner of a hoop being trundled. Although 

 it is hardly necessary to say that there is no truth 

 in the statement, yet a certain parasite of the bat 

 does proceed by rolling over and over, Tennent 

 recording that the creature moves ' by rolling itself 

 rapidly along, rotating like a wheel on the extremi- 

 ties '' its spokes, or like the clown in a pantomime 

 hurling himself forward on hands and feet alter- 

 nately. . . . Its speed exceeds that of any known 

 insect, and as its joints are so flexible as to yield in 

 every direction ... its motions are exceedingly 

 grotesque as it tumbles through the fur of the bat.' 



Turning our attention to those creatures which 

 are only able to crawl, we find that the snakes and 

 the legless lizards walk as it were upon the extremi- 

 ties of their ribs, assisted by the projecting edges of 

 the scales upon the under surface of their bodies, 

 which offer a resistance to any rough smrface that 

 they may happen to come into contact with. 

 Should, however, one of the reptiles be placed upon 

 a sheet of glass, it is perfectly helpless. When 

 crawling along, snakes invariably move their bodies 

 in lateral wave-like motions, and never in vertical 

 undulations, as one frequently sees depicted in 

 illustrated books. 



The common earthworm indulges in yet another 

 form of locomotion, for by alternately contracting 

 and expanding the segments of its body the creatiue 

 forces itself along, aided by the numerous minute 

 hairs which project from the skin. 



