142 MISS MARION I, NEWBIGIN. 
their attachment rather than to cling more closely; but in 
their case the shell is coiled, is large enough to admit of 
the whole animal being withdrawn into it; and further, the 
foot carries an operculum or shutter by means of which the 
mouth of the shell can be closed. This operculum not 
only protects the animal from attacks, but also prevents the 
evaporatiou of water, and so diminishes the risk of drying 
up. 
Limpets and periwinkles may be taken as types of those 
shore animals which protect themselves from the danger of 
drying up by their thick shells, which also protect them 
from the force of the waves and the other untoward in- 
fluences of shore life. So well sheltered are they that they 
make no attempt to hide themselves from the summer suns 
or the frosts of winter, but may always be seen fully ex- 
posed to view whenever the tide ebbs. But everyone 
knows that it is only relatively few animals which expose 
themselves so freely, most have to be searched for diligently. 
If this aspect of the matter has never struck you, you will 
find it instructive to take a faunal list, such as Herdman 
and Leslie’s Fauna of the Forth, and go down with it to the 
shore and see how many of the animals named in it you can 
find without an elaborate search. If we prohibit stone- 
turning or the lifting up of weed, your list will, I think, 
be short enough. In other words, relatively few animals 
are hardy enough or well protected enough to expose them- 
selves freely; most seek concealment, shelter both from 
their physical and their, organic environment. The means 
of concealment are many; we can look only at a few of 
them. One of the most effective is perhaps the habit of 
burrowing. A burrowing animal obtains protection from 
the waves, save in great storms. It obtains permanent 
moisture, a more or less even temperature, and is safe from 
the versecution of most organic foes. The list of benefits 
is so long that it is no wonder that so many different kinds 
of animals have acquired burrowing habits. We can 
mention only a few of them. If you stoop under over- 
hanging ledges of rocks, or turn over weed-incrusted stones, 
you may often see numerous round holes from each of 
which a bright red star protrudes. Touch the stars and 
