In many tropical Frogs the reproductive habits are much modified. One species (_Phyllobates trinitatis_) of Venezuela and Trinidad carries its tadpoles on its back, to which the young attach themselves by means of their suckers. A frog of the Seychelles Islands lives in the tree-ferns far from water, and carries its young about on its back, to which they are attached by their bellies. In the Kameruns lives a Frog that lays its eggs in a foamy mass on the leaves of a tree. When the larvae are developed the mass becomes slimy and the tadpoles swim about it, and when a heavy rain falls they are washed into pools of water lying at the bases of the trees. The foam is probably produced as it is in culinary operations, by air being entangled in it by a beating that the Frog gives the jelly with its feet. The inclosed air may well serve in respiration. Compare TOAD. UTILITIES. Among both civilized and savage men Frogs are a culinary dainty. The edible European Frog is so much prized in France that it is bred for the market in large preserves. In the United States both the Bullfrog and spring Frog are sold in the markets. In France and the United States the hind legs alone are eaten; they are known as "saddles" to American marketmen, and are usually served at table fried. In Germany all the muscular parts are served stewed, often with sauce. Frogs have enabled man to contribute much to his knowledge of physiology. The tail of the tadpole, so frequently fed on by dragon-fly larvae and other aquatic enemies, has great capacity of regeneration. The study of its re-formation has added to our knowledge of the regeneration of animal tissue. The circulation of the blood, so readily seen by the aid of the microscope in the web of the Frog's foot, is a classic and painless classroom demonstration. Observations on the response of Frog-muscle to stimuli led the great Italian physiologist Galvani to the discovery of dynamical or current electricity, known to us as galvanic or voltaic electricity. [Illustration: THE MALE FROG. (See Blower.)] Nests and Nest Building. Whenever the spawning period occurs, ample warning will be given, as the male Frogs will begin croaking for their mate, and will be seen near the shore. Early in the spring is the breeding season, and the Frogs will be seen in pairs, working in company, selecting nests, which are in place where there is a vegetation to attach the spawn, near the surface of the water, as the action of the sun has much to do with the hatching of the spawn.