150 THE THREE-SPINED STICKLEBACK 



are their instruments both of offence and defence, 

 and are always erected on the least appearance of 

 danger, or whenever they are about to attack other 

 fish. The body near the tail is somewhat square, 

 and the sides are covered with transverse bony 

 plates. Their usual colours are olive green above, 

 and white on the under parts ; but in some indivi- 

 duals the lower jaw and the belly are of a bright 

 crimson. 



By feeding with great voracity on the fry and 

 spawn of other fish, they are, notwithstanding the 

 smallness of their size, greatly detrimental to the 

 increase of -almost all the species among which they 

 inhabit. One that Mr. Arderon of Norwich had 

 in a glass devoured in five hours no fewer than se- 

 venty-four young dace, each about an inch and a 

 half long, and of the thickness of a horse-hair, and 

 would have done the same every day, had they been 

 given to it. 



The fish was put by Mr. Arderon into a glass 

 jar of water, with some sand at the bottom for the 

 purpose of trying some experiments on it, as well 

 as for the purpose of ascertaining its manners, as 

 far as possible in a confined state. For a few days 

 it refused to eat ; but by frequently giving it fresh 

 water, and by coming often to it, it began to eat 

 the small worms that were now and then thrown 

 into the jar; soon afterwards it became so familiar 

 as to take them from the hand; and at last it even 

 became so bold, as, when it was satiated, or did not 

 like what was offered to it, to set up its prickles and 

 strike with its utmost strength at the fingers, if put 



