256 POPULAR HISTORY OF THE AQUARIUM. 



which was kept in water three years and a half, fed with 

 raw beef, destroyed a specimen of llijdrous plceus, wliich 

 was twice its own size, piercing it with the jaws on the 

 only vulnerable point, namely on the under side, at the 

 insertion of the head and thorax, and so sucking its 

 juices. Esper observed that a D. marc/inalis so completely 

 sucked the blood out of the pieces of meat it was fed with, 

 that they looked like small masses of white, floating on the 

 surface. 



They ascend frequently to the surface for the purpose of 

 breathing, and would sometimes almost appear as if they 

 were performing that operation through their tails ; for they 

 lie immersed all but the hinder extremity, which protrudes 

 from the surface. Here they appear at rest, balancing on 

 their oar-legs, which are stretched at right angles. Al- 

 though pretty constant denizens of the pool, they cannot 

 remain without occasional access to the air; and sometimes, 

 creeping up the rushes to take flight, they mount up in the 

 air perpendicularly, like the lark, till out of sight. The de- 

 scent is equally direct, resembling rather a fall than a flight. 

 It is stated that they are guided in their descent by the 

 reflection of light upon the water's surface ; for they have 

 sometimes been deceived and have fallen with violence upon 



