Ob METAMORPHOSES OF MAN 



kindred genera. In this group we meet with both 

 complete and incomplete metamorphoses; but here 

 we find them marked by quite different features from 

 those we saw among insects. The changes do not 

 appear to take place- suddenly, nor is there anything* 

 like the apparently torpid condition of the pupa. All 

 the transformations take place gradually, and as far 

 as the external organs are concerned, the development 

 may be closely watched by the observer. 



The development of frogs presents another curious 

 phenomenon quite different from what we have already 

 seen. It is this : the young animal, after it has left 

 the egg, and before it has become a larva, is still 

 in a semi- embryonic condition. At this period the 

 digestive tube and its appendages are exceedingly 

 rudimentary. The greater portion of the body is 

 filled by a large mass of yolk or vitellus, inclosed by 

 the skin, which has been formed for some time ; and 

 it is at the expense of this alimentary matter that the 

 development proceeds. 



The external characters are in keeping with the 

 imperfect condition of the animal at this period. The 

 head is large, and appears to be divided in two on 

 the under surface, each half being prolonged as a 

 sort of process by which the animal attaches itself 

 to surrounding objects; as yet there are no traces 

 of either eyes, nostrils, respiratory or auditory organs ; 

 and the belly, of an oblong form, is continued pos- 

 teriorly as a short tail bordered with a riband-like 

 membrane. This primitive condition, however, does 

 not last long. About the fourth day after birth, the 

 head, which is now as long as the body, has somewhat 

 the appearance of a thimble ; the mouth is provided 



