METAMORPHOSES. 227 



passes before it acquires its full complement of limbs. 

 Even before we take leave of the Vertebrates, there are 

 extraordinary examples of such transformations. Thus 

 in the race of Frogs : the young, or tadpole, is deficient 

 in limbs, swims like a fish, and breathes through gills ; 

 while the full-grown animal is, as every one knows, fur- 

 nished with nimble and well-formed legs, and breathes 

 through lungs. One can scarcely conceive a greater 

 change in organization than is here displayed before 

 our eyes. It strikes us as wonderful, because the young 

 of other Vertebrates exhibit no such change after birth ; 

 and yet it would appear, from the researches of anato- 

 mists, that before birth the foetus of all, not excepting 

 that of man himself, undergoes changes of an analogous 

 nature. So that here, as everywhere, Nature vindi- 

 cates her uniformity. All of the vertebrate class are 

 destined to go through a certain round of changes, 

 but in some a portion of these changes take place 

 before birth, in others after it. 



Leaving the Vertebrates, in which transformation of 

 the young after birth is the exception, we reach the 

 Articulate or Insect races, in which it becomes the rule. 

 All are familiar with the quadruple state under which 

 insect-life appears, the egg, the grub or caterpillar, 

 the chrysalis, and the perfectly-formed insect. In these, 

 as in the Frog, we find the young animal fitted for a 

 condition of life totally different from that to which 

 its mature state is destined ; and, in many cases, the 

 difference in its breathing apparatus is equally great. 

 The young of many insects, as of the Dragon-flies and 

 Gnats, live under water until their last change, when, 



