OR, THE HOME-CULTURE OF FRESH-WATER PLANTS. 
its victim. They are also pursued and devoured by 
the voracious Water Beetle (. Dyticus marginalis), 
whose horny forceps defy the armour and spinal 
defences of this formidable little fish. 
Block states that the duration of the life of the 
Stickleback is three years ; and the observations of 
other naturalists appear to confirm this opinion. 
Mr. Yarrell divides the genus Gasterosteus into 
several species, all of which are tolerably well 
marked. The first is termed G. trachurus , or 
Bough-tailed Stickleback; his defensive plates of ar¬ 
mour continuing all along the side to the tail, upon 
which they appear to terminate in minute spines. 
The second is called G. semiarmatus , or half-armed, 
his defences not continuing above three plates be¬ 
yond the pectoral fin. The third, G. leiurus , or 
Small-tailed Stickleback, the side plates being less 
conspicuous and not extending beyond the pectoral 
fin. The fourth, G. brachycentrus , or short-spined 
kind, as large as the first or second species named, 
but having the spines on the back much shorter. 
The fifth has been termed G. spinulosus , the four- 
spined species, much smaller than the last named. 
Probably from feeling himself more completely 
armed, however, he is more decidedly pugnacious 
than his larger relatives, even in confinement. The 
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