THE WONDERS OF THE SHORE. 201 
see it mown off every morning as fast as it grows, 
in little semicircular sweeps, just as if a fairy’s 
scythe had been at work during the night. 
And a scythe has been at work; none other than 
the tongue of the little shell-fish; a description of 
its extraordinary mechanism (too long to quote here, 
but which is well worth reading) may be found in 
Gosse’s “Aquarium.””? 
A prawn or two, and a few minute star-fish, will 
make your aquarium complete; though you may 
add to it endlessly, as one glance at the salt-water 
tanks of the Zoological Gardens, and the strange 
and beautiful forms which they contain, will prove 
to you sufficiently. 
You have two more enemies to guard against, 
dust, and heat. If the surface of the water becomes 
clogged with dust, the communication between it 
and the life-giving oxygen of the air is cut off; and 
then your animals are liable to die, for the very 
same reason that fish die in a pond which is long 
frozen over, unless a hole be broken in the ice to 
1 P. 34. Figures of it are given in Plate VIII. 
