Page:Natural History, Reptiles.djvu/252

244 sooner in warmer climates, the little Tadpoles are hatched. They appear to consist of an enormous head and a long, thin, vertically flattened tail; from the hinder part of the head, on each side, are seen to project two minute tufts, divided into branched leaflets. These are the branchiæ or gills, by means of which oxygen is separated from the water for the renewal of the vital power of the blood. These tufts rapidly enlarge, and soon attain their greatest development, in which state they form, as Mr. Bell assures us, one of the most charming objects for microscopic observation which can be conceived, and to view which a very high power is not necessary nor even desirable. The current of the blood poured in regular pulsations at each contraction of the heart, passes up each stem or main branch of the branchiæ, and a distinct stream is given off to each leaf; it is propelled to the extremity, and

then returns down the opposite sides in the most regular manner, and the parts are so transparent