92 OUR REPTILES. 



bodies, enclosed in a glairy mass, are deposited at 

 the bottom of pools and ditches. Speedily, by the 

 absortion of water, the envelope swells, and each 

 ovum, like a little black dot, is enclosed within its 

 sphere of gelatine. These masses of ova soon rise 

 and float on the surface of the water, in which state 

 they are known to all country people as " frog 

 spawn." 



At first the embryo is a small globular body, 

 rather darker on one side than the other. In about 

 four-and-twenty hours the sphere elongates, and in 

 eight-and-forty hours the presence of a head and 

 tail may be distinguished. Gradually the fin 

 appears around the tail, and the rudiments of the 

 branchiae, in the form of tubercles, project from 

 each side of the neck. Within about four days 

 from the deposit of the ova, in a warm climate, 

 such as Italy, the membrane is ruptured and the 

 tadpoles become free ; but in our own clime a much 

 longer period is required, and the eggs are not 

 usually hatched for a month after their deposition. 



Soon after the emergence of the tadpoles from 

 the egg, the branchice, or extended gills, attain 

 their full development, when they gradually diminish 

 in size, until at length they become withdrawn into 

 the cavity prepared for their reception, and are 

 closed by a fold of the skin. For some time the 

 tadpoles continue to grow day by day, and increase 



