THE MAILED WARRIORS OF THE SEA. 159 
great group of " Crustacea," the " insects of the sea." 
For though some of this group, as the water-flea and 
cray-fish, live in rivers and ponds, while a few, such 
as the wood-louse and even some kinds of crabs, 
crawl upon the land, yet the chief home of the Crus- 
tacea is the ocean, where, having scarcely any enemies 
so powerful as themselves except their own relations, 
they run riot both as to numbers and size. Think 
for a moment of the multitudes of sandhoppers to be 
seen leaping on a dry sandy shore in the evening, 
or which rise like a cloud of dust out of the half- 
rotten seaweed if you stir it with your hand. Try 
to reckon up the myriads of shrimps and prawns 
which must be caught daily to supply all England, 
and which are nothing to those that remain behind. 
Look at the large crabs and lobsters in the fish- 
mongers' shops, and think that in London alone 
25,000 lobsters are often sold in the season in one 
single day ! Then call to mind how you cannot 
walk a step on the shore at low tide, without seeing 
some tiny crab scuttling along in a hurry to catch 
something, or to escape being caught himself; or 
how constantly you come across a hermit crab with 
a periwinkle or whelk shell on his back, making 
tracks in the sand as he wanders along. Try and 
count some day the number of acorn shells (Fig. 61, 
p. 174) which grow on one single piece of rock or 
the groyne of a pier. For these too are crustaceans, 
as are also the barnacles (Fig. 61) which hang from 
floating timber or gather on the bottom of ships. 
When you have gained some idea of the multitudes 
of these creatures on our own shores, you will net 
have reckoned one millionth part of the crustaceans 
