1380 THE STORY OF THE UNIVERSE 



velopment. Preparations are silently making for a 

 change of habitation, for the animal's emerging 

 from the waters, for the reception of atmospheric 

 air into new cavities, for the acquisition of limbs 

 suited to new modes of progression; in a word, for 

 a terrestrial life, and for all the attributes and powers 

 which belong to quadrupeds. The succession of 

 forms, which these metamorphoses present, are in 

 themselves exceedingly curious, and bear a remark- 

 able analogy with the progress of the transforma- 

 tions of those insects, which in the first stages of 

 their existence are aquatic. To this philosophic in- 

 quirer into the marvelous plans of creation, the series 

 of changes which mark these singular transitions 

 can not fail to be deeply interesting; and occurring, 

 as we here find them, among a tribe of animals allied 

 to the more perfect forms of organization, they 

 afford us a better opportunity of exploring the secrets 

 of their development by tracing them from the 

 earlier stages of this complicated process, so full of 

 mystery and of wonder. 



The egg of the frog is a round mass of transparent 

 nutritive jelly, in the centre of which appears a 

 small black globule. By degrees this shapeless 

 globule exhibits the appearance of a head and tail, 

 and in this form it emerges from its prison, and 

 moves briskly in the water. From the sides of the 

 neck there grow out feathery tufts, which float 

 loosely, and without protection, in the surrounding 

 fluid. These, however, are mere temporary organs, 

 for they serve the purposes of respiration only until 

 the proper gills are formed, and they then shrink and 



