Page:British Reptiles, Amphibians, and Fresh-water Fishes.djvu/56

BRITISH AMPHIBIANS to the bottom, but as the gelatinous substance with which they are surrounded begins to swell, and thus becomes lighter and more buoyant, the mass of spawn rises to the surface where the warmth of the sun, with the gracious influence of light and air, helps to complete the hatching process. As soon as the dark chocolate-coloured tadpole emerges (and the egg can easily be observed changing shape within the transparent jelly-sphere), it is the owner of external gills, and a fringed sucker on the under part of the head enables it for a time to cling to any surrounding object. In due course the external gills are exchanged for internal ones, and the sucker is discarded, there being no further use for it. The head becomes bull-dog like, the mouth is formed, and the hind limbs appear. The front pair of limbs poke through last of all as, until they emerge, they remain hidden within the gill-chambers. After several weeks, the internal gills disappear, lungs are formed, and the tadpole comes to the water-surface to take in air. It is a vegetarian in diet up to now, but there comes a time when it seems to lose its appetite, and perhaps there is small wonder for this when one realises the wonderful changes taking place both within and without. The tail becomes shorter, the mouth widens, the lip-frills wither, the horny jaws disappear, the eyes pierce the skin, the front pair of legs poke through, and these things completed, the tadpole commences to feed again. But, meanwhile, it has ceased to be a vegetarian, indeed has developed the ways of a cannibal, as it will readily 40