COLORATION OF LAND SNAILS. 



189 



color of the animal corresponds with the prevailing color of the 

 environment, and thus it escapes the notice of its enemies. 



A more complex state of affairs exists in those animals which 

 make use of external objects for their own concealment. A case 

 in point is the hairy snail (Helix hirsuia), a species commonly 

 found throughout the Northern States, living around decaying 

 logs in the forests. These little fellows have a clothing of short 

 hair all over the shell, and this hair holds so much of the soil 

 that they look more like small pellets of earth than like snail- 

 shells. The disguise is effective enough to deceive more acute 

 shell-collectors than the birds. 



An altogether similar attempt at 

 deception is practiced by a marine 

 mollusk, the so-called " carrier." 

 This gastropod has a broad spiral 

 shell, to the upper surface of which 

 it cements shells or pebbles, until 

 finally it ajjpears to be nothing more 

 than a heap of shell-fragments, not 



distinguishable from any other irregularity of the sea-bottom. 

 Another instance may be mentioned, as it illustrates the exten- 

 sion of this general principle to widely different groups of ani- 

 mals. The sea-urchins of our coasts have often been observed to 

 cover themselves completely with small stones, so that nothing 

 can be seen but a heap of pebbles. 



Coming back to our hairy Helix, we may perhaps credit its 

 hirsute coat with an additional function besides mere dirt-gather- 

 ing. Poulton has observed that some insectivorous animals have 

 an excessive repugnance for hairy insect larva?, even when they 



Fig. 1. — Helix hirslta. Showing 

 hairy cuticle. 



Fig. 2. — Three-toothed Snail, Helix tri- Fig. 3. — Caracolus labyrintihs — a South 

 dentata. Illustrating the simplest form American forest snail. Showing extreme 



of obstructing teeth. development of lip-teeth. 



are not otherwise repulsive. The marmoset, for instance, can not 

 be induced to touch any hairy larva. It is not improbable that 

 small mammals, such as moles and field-mice, find the hairy 

 covering of Helix hirsuta disagreeable, although we know that 

 they eat other snails. 



An old collector, who had spent most of his life within the 



