676 



PHYLUM CHORDATA : CLASS AMPHIBIA 



yet have been beneath the skin, become exposed ; the 

 fore-hmbs appear, the left one being pushed through 

 the spout-hke opening of the branchial chamber, and the 

 right one forcing its way through the opercular fold, in 

 which it leaves a ragged hole " (Marshall). 



While these changes are in progress, and as the supply of 

 food afforded by the tail begins to be exhausted, the tadpole 

 recovers its appetite, but is now exclusively carnivorous, 



Fig. 388. — Life-history of a frog. — After Brehm. 



1-3, Developing ova ; 4, newly hatched forms hanging to water- 

 weeds ; 5, 6, stages with external gills ; 7-10, tadpoles during 

 emergence of limbs ; 11, tadpoles with both pairs of limbs appar- 

 ent ; 12, metamorphosis to frog. 



feeding on any available animal matter, or even on its 

 fellows. The change is not, however, so great as it seems, 

 for even at a very early stage animal food is eagerly 

 devoured. 



With the change of diet, the abdomen shrinks, stomach 

 and liver enlarge, the intestine becomes relatively narrower 

 and shorter. The tail shortens more and more, and as it 

 does so the disinclination for a purely aquatic life seerns to 

 increase. Eventually it is completely absorbed, the hind- 

 limbs lengthen, and the conversion into a frog is completed. 



