THE AMPHIBIANS 



183 



plex internal organs adapt the animal to a free-swimming 

 existence for days to come. 



The tadpole is now, to all intents and purposes, a fish 

 a fact most clearly recognized in its form, method of loco- 



FIG. 108. Metamorphosis of the toad. Partly after GAGE. 



motion, the arrangement of the gills, and the general plan 

 of thj^circulatory system. 



JJ^rFurther growth. In the course of the next few 

 weeks hind limbs develop beneath the skin, through which 

 they finally protrude. In the same manner, fore limbs arise 

 at a later date. In position these organs are like the paired 

 fins of fishes, but they are intended for crawling or leaping 

 on land, and are modified in accordance with this need. As 

 in the higher vertebrates, the limbs develop as arms and 

 legs, with long fingers and toes, between which are stretched 

 webs of skin, which serve in swimming. 



