instinct. Among Crustaceans the instinct in its fully developed form is quite uncommon. Some years ago I described the death-feigning of certain species of terrestrial amphipod crustaceans which are frequently found on sandy beaches near the seashore. On account of their peculiar hopping movements these crustaceans are commonly known as sand-hoppers or sand-fleas, although they have of course no relation to the ordinay fleas of human experience. One of the largest species of sand-hopper, Talorchestia, is common along our Atlantic coast, where it lives during the day in burrows made in the sand, coming out only at night to feed upon the seaweed and other material washed ashore by the waves. When the Talorchestias are dug out of their burrows,
they usually lie curled up with their long antennae bent under the body and their legs drawn up so as to assume a compact form. They will lie in this way for several minutes, when they may be seen slowly to relax; the legs then move about, and soon the creature hops away by a sudden extension of its abdomen. When caught in the hand they will feign death again, and repeat the performance many times in succession. Other species of sand-hoppers exhibit the same instinct, though less perfectly, and there are traces of it in many of the reactions of their aquatic relatives.
The various species of wood lice exhibit the instinct of feigning death in various degrees. Some species are able to roll up into an almost perfect ball and will remain in that state for a considerable time. Other species curl up, but make only a very imperfect approximation to a sphere, and they may not maintain this attitude but for a short period. Some myriapods when disturbed curl up in much the
