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 



FIG. 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 la,nd animal. On land the toad lives, as 



