ISOPOD AND AMPHIPOD CRUSTACEANS. 383 



ceans rather for the purpose of warning the aquariist 

 against their destructive ravages than of recommend- 

 ing them as objects fit for admission into his tanks, 

 except for the purpose of specially investigating their 

 own habits, some of which are sufficiently remarkable. 



Of these, myriads may be met with on turning 

 over any heap of sea- weed left upon the beach by the 

 receding tide jumping about in all directions like 

 so many grasshoppers, and that with such activity, 

 that, out of hundreds which may be skipping about, 

 the collector will be lucky in catching two or three 

 individuals ; in fact, the capture of these creatures is 

 one of those exceptional pieces of business that can 

 only be done well when done in a hurry. The mode 

 in which these animals leap is curious. To execute 

 their active movements, they bend under the body 

 certain appendages belonging to their tails, and then, 

 suddenly letting them go like a spring, they are 

 thrown into the air by the jerk, just upon the prin- 

 ciple of the " skip-jacks " with which children amuse 

 themselves. When placed in the water, they swim 

 about by means of the contractions of their tail, 

 aided by the movements of their feet ; and some, in 

 consequence of the extreme compression of their 

 body, and the very strong curvature of the tail, are 

 obliged, when at rest, to remain continually couched 

 on one side. 



The Sand-hoppers live on animals smaller than 

 themselves, or on dead bodies cast on shore by the 

 waves; they are themselves eagerly devoured by 

 aquatic birds, and form an excellent bait for taking 

 small fishes by the line. They carry their eggs under 



