COMMON PROG. 89 



esting. As in the Toad, the tongue is doubled back upon 

 itself when at rest ; and being embued with a viscous secre- 

 tion at the extremity, it is suddenly thrown forwards upon 

 the insect, which, being caught by the adhesive matter upon 

 it, is instantly drawn into the mouth by the sudden return 

 of the tongue to its former position, and is then swallowed. 

 This is but the work of an instant ; and, indeed, is performed 

 with such rapidity, as scarcely to be detected without careful 

 watching. 



Like the rest of the Amphibia and the Reptilia, the Frogs 

 retire, on the approach of winter, to their hibernating re- 

 treats, where they pass the dreary season in a state of absolute 

 torpidity. This is generally in the mud at the bottom of 

 the water, where they are not only preserved in a nearly 

 equal temperature, though at a low degree, but also secured 

 from external injury. Here they congregate in multitudes, 

 embracing each other so closely as to appear almost as one 

 continuous mass. On the return of spring they separate from 

 each other, emerge from their places of retirement, and re- 

 commence their active life by exercising the important 

 function of the reproduction of their species. Here we enter 

 upon the most interesting scene in the history of these 

 animals ; for it is here that the peculiar characters which 

 distinguish them from all other forms, are most strikingly 

 shown ; and I shall, therefore, enter somewhat in detail into 

 the different steps of the developement of the embryo, and of 

 the changes which take place in the structure and habits of 

 the young animal as it advances towards its perfect con- 

 dition. 



The impregnation of the female Frog is effected in a pecu- 

 liar and very remarkable manner. Whilst in the reptilia, 

 as in most of the superior vertebrate animals, as well as in 

 many of the lower classes, the application of the vivifying 

 fluid to the ova, is rendered certain by actual insertion within 



