Marvels of the Universe 603 
Ws SUFINMVIMNVEIZS (Ol SNAWES 
BY BERNARD C. WHITE 
PROTECTIVE resemblance is a method of self-preservation that widely prevails in the world of 
Nature. It is well known to be frequently adopted by beasts and birds, and, above all, by insects ; 
but it is not so widely known that it is also in vogue in the world of molluscs. 
A remarkable instance is mentioned by Karl Semper. The Snail was Xesta, which was 
found to mimic the markings of another snail, Helicarion. Now Helicarion possesses the power of 
shaking off the tail when seized or irritated, and so of escaping from the clutches of its enemies. 
The result is that these enemies, finding the game of hunting it not worth the candle, leave 
Helicarion unmolested. Xesta has recognized its neighbour’s immunity from attack, and has 
adopted the appearance of Helicarion, although it is unable to shed its tail at will. However, 
as it lives associated with Helicarion, the deception is sufficient to safeguard it from attack. 
Two splendid examples of protective coloration are furnished by the Common Limpet and 
the Blue-rayed Limpet. In the first, its colour exactly resembles the surface of the rock on which 
it lives, and when the edges of the shell are drawn down to fit tightly into its shallow hollow in the 
rock, the creature looks for all the world like a rough protuberance of the rock itself. In the case 
of the Blue-rayed Limpet, the young Snail feeds on the iridescent leaves of one of the larger 
sea-weeds, and is possessed of an oval, thin, semi-transparent shell, ornamented with vivid blue 
lines running from the beak to the margin, and can hardly be distinguished from its food-plant. 
But in later life it prefers the rounded stalk, and finally the roots of the seaweed, which are 
entirely devoid of iridescence. It therefore adapts itself to its newly-chosen surroundings. The 
shell becomes thickened and compressed at the sides; the hitherto smooth, sharp base assumes 
a shape which will accurately fit the stalk. The blue lines are no longer wanted—in fact, 
would make their owner conspicuous—and so disappear, and the shell loses all resemblance to 
its former self. The mature Limpet now scoops out a little cavity in the seaweed, and 
becomes actually part of the root or stem. 
Photo by) [V. J. Ward. 
CARRIER SHELLS. 
In order to save himself from the attacks of enemies the Carrier Snail hides his shell under a coating of cement, to which he 
attaches any pieces of rock or shell that come his way. As a result his home has only the appearance of a mass of 
rubble. 
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