326 



ICHTHYOPSIDA 



rounded by gelatinous discs, the black ovum (fig. 167, 1) being 

 seen as a small round body in the middle. The young (3) when 

 hatched and free from the gelatinous envelope attach themselves 

 by two suckers to the jeUy of the spawn. The young Tadpoles 

 are very like " tailed amphibia," and in their earliest stage have 



Pio. 167. — Development of the Pbog. 



1 and 2, Ova; 3-5, tadpoles; 6, period when i5rst pair of legs form (posterior pair) ; 

 7, both pairs of legs present (Urodela stage) ; 8, tail disappearing ; 9, adult frog. 

 (Nicholson.) 



both internal and external gills (4). The tail is long, thin, and 

 fish-like, but there are no fin-rays. The external gills soon dis- 

 appear. The upper and lower jaws become hardened, and form 

 a kind of beak. By degrees small bud-like outgrowths appear 

 between the body and tail, which grow out into the hind-limbs 

 (6), which are always the first to appear in the Frogs and Toads, 



