row in the ground, or in clefts of rocks, for their winter sleep. We once saw twenty-six black snakes taken from one burrow beneath the roots of a partially-fallen tree, in February. Other observers have found a much larger number. We are informed that more than 300 have been found in a single burrowing-place, and that many species, venomous and non-venomous, sometimes resort to the same rendezvous and hibernate together. In the tropics the anaconda (Fig. 6), and perhaps other species of serpents, sometimes hibernate during the dry season of summer in the hardened mud of dried-up pools. It is by the power to hibernate that serpents survive during the winters of temperate climates, but they seem unable to withstand the extreme and long-continued cold of the arctic zone. There, serpents, and indeed
reptiles of all kinds, are rare, and frequently are entirely wanting. In the Falkland Islands, Terra del Fuego, and the mountains of Southern Patagonia, no serpents have been found. The persistence of vitality in serpents is extraordinary, and continues after great mutilations. They are said to have lived several days after removal of the head and viscera. One placed in a vacuum twenty-four hours still showed signs of sensibility; and, many hours after decapitation, a rattlesnake would plunge its headless trunk as in the usual act of striking.