THE FROG'S YEAR 51 



their life began that is, after the eggs at the 

 moment of being laid were likewise fertilized. 



Peculiar half-finished little creatures the newly- 

 hatched larvae are mouthless, limbless, blind, 

 covered with microscopic cilia, with just the be- 

 ginnings of a first set of gills. They attach them- 

 selves by a horseshoe-shaped cement-organ to water 

 weed, and subsist for some time on a legacy of 

 yolk. It is an often-told story how these newly- 

 hatched larvae develop into true tadpoles, with open 

 mouth, gill-clefts, and a second set of gills; how 

 the limbs bud out; how the lungs develop and the 

 two-month-old pollywogs learn to use them, taking 

 gulps of air at the surface; how the circulation 

 changes from a piscine to an amphibian type; and 

 ,how after nearly three months have passed there 

 is a striking metamorphosis, the outcome of which 

 is a tiny frog. The substance of the tail is broken 

 up, and dissolved as if a pathological process had 

 become normalized; the amoeboid phagocytes which 

 play such an important role in inflammation have 

 their share in changing the tadpole into a frog, 

 now acting as sappers and miners, and again as 

 transporting agents. The mouth changes its char- 

 acter entirely; the tongue, hitherto small, increases 

 notably; the eyes, hitherto beneath the skin, reach 

 the surface at last. It is time for the young frog to 

 get ashore, else it will drown. It has been shown 

 experimentally that not even the common water- 

 frog can live under water for more than ten minutes, 



