LECTURE VII. 23 



groupes or clustered masses; each egg being of 

 a gelatinous substance, perfectly transparent, and 

 containing the young animal in its centre under 

 the form of a round black globule. In the space 

 of about a month the globule assumes an oval 

 shape, and soon after hatches ; not in the form of 

 a complete Frog but of what is termed a tad- 

 pole, and appearing, on a general view, to con- 

 sist merely of head and tail; the former black 

 and large, the latter slender, and bordered with 

 a transparent finny margin. The motions of the 

 tadpoles are very lively, and in the advanced state 

 of Spring are so plentiful that the waters they 

 inhabit appear blackened by their numbers. They 

 live on the leaves of the plant called duckweed 

 and on other small vegetable substances: during 

 the early part of their growth they are furnished 

 on each side the head with a pair of ramified 

 breathing organs, which drop off when they are 

 farther advanced in age; and when they have 

 arrived at the ag of five or six weeks, the hind- 

 legs make their appearance, and soon afterwards 

 the fore-legs. Some time after this the tail begins 

 to decrease, and at length becomes quite obli- 

 terated. The animal now ventures upon land, 



