250 HISTORY OF BRITISH ZOOPHYTES. 
stand it in good stead, for they have the power of causing 
to adhere to them sand and gravel, and fragments of shells, 
so that the body is quite covered. This, it is probable, 
answers a double purpose. By this covering, the animal, 
when left by the tide naked, is defended from the scorching 
beams of the sun; it answers nobly also the purpose of 
concealment. ‘That kind Providence which cares for the 
inferior animals, furnishes various means of eluding their 
enemies. The ptarmigan, which inhabits the lofty mountains, 
gets white plumage when winter returns, so that even the 
keen-eyed eagle can scarcely distinguish it from the snow- 
clad peaks among which it dwells. Were the alpine hare 
to be white in summer, it would be too conspicuous when 
skipping along the heath; and it would be not less so in 
winter, when all is white around, were its fur not to lose its 
summer hue, and to become white as the mountain snow. 
Nothing could be better fitted to conceal this Actinia, which 
abounds on our shores, than this very covering with which 
it knows so well how to clothe itself. When the ebbing 
tide leaves the sand-covered rocks dry, a sea-anemone of so 
large size, even when contracted, would be very observable. 
But when its tentacula are all retracted, and the warty skin 
covered with the sand and shelly fragments that so firmly 
