THE LIFE CYCLE 95 
the microscopic plants to be found in the water, and swim 
easily about by means of the long tail. The very young 
tadpoles remain underneath the surface of the water all the 
time, breathing the air which is mixed with water by means 
of gills. But as they become older and larger they come 
often to the surface of the water. Lungs are developing 
inside the body, and the tadpole is beginning to breathe as 
a land animal, although it still breathes partly by means of 
gills, that is, as an aquatic animal. Soon it is apparent that 
although the tadpole is steadily and rapidly growing larger, 
its tail is growing shorter and smaller instead of larger. At 
the same time, fore and hind legs bud out and rapidly take 
Fia. 46.—Metamorphosis of the toad (partly after Gage). At left the strings of eggs, 
in water the various tadpole or larval stages, and on bank the adult toads. 
form and become functional. By the time that the tail 
gets very short, indeed, the young toad is ready to leave the 
water and live as a land animal. On land the toad lives, as 
