THE MAILED WARRIORS OF THE SEA. 173 
has its hind feet broad and flat, and may be seen 
swimming, when the common crab can only creep ; 
while the oceanic crab has taken to the open sea, 
and can swim for days without resting, feeding the 
while. Then, on the other hand, there are crabs 
living on the land. The racing crab of Ceylon, 
which will outstrip the swiftest runner, burrows in 
the dry sand ; and though it likes to have its gills 
moist, dies if held under water. The frog-crab of 
the Indian ocean climbs on the roofs of houses ; 
the robber crab of the Mauritius lives in holes lined 
with cocoa-nut fibre at the roots of the cocoa-nut 
palm, and breaking open the nuts feeds upon the 
fruit ; while the land-crab of the West Indies burrows 
in the ground, and goes only once a year to the sea 
to lay her eggs. Still all these crabs retain enough 
of their old habits to like to have their breathing- 
gills wet, and most of them visit water daily for this 
purpose, while some of them have a curious way of 
keeping the water enclosed, and freshening it with 
air, while others use the water till it is exhausted, 
and then raise their shield or carapace and breathe 
as land animals. 
And now after hearing of these land crabs, we 
shall not find it so difficult to believe that the little 
wood-louse of our gardens, which curls itself up like 
a ball, and is the only form we have remaining like 
the huge trilobites of ages gone by, is a true crus- 
tacean, adapted for breathing air though still loving 
moist places. 
But we must return to the sea, where a most 
curious and interesting group still remains for us to 
study. We have heard of old families among men, 
