THE AMPHIBIANS 177 



In geological times many of the salamanders were of 

 great size, several feet in length, and some were enclosed 

 in an armor consisting of bony plates. All now living have 

 the skin naked, and with the exception of the giant species 

 of Japan, three feet in length, and a few similar forms in 

 America, the modern representatives are comparatively 



FIG. 108. Blunt-nosed salamander (Amblystoma opacum). Photograph by W. H. 



FISHER. 



feeble and measure their length by inches. Only a few, on 

 account of their bright colors, are particularly attractive, 

 while the others are usually shunned and considered re- 

 pulsive, chiefly because of their supposed poisonous char- 

 acter, though in reality few animals are more harmless. 



169. Tailless forms. In the frogs and toads the meta- 

 morphosis which the young undergo is almost as profound 

 as that which takes place with the insects. The gills, to- 

 gether with their blood-vessels, disappear completely. The 

 tail, with its muscles, nerve-supply, and skeleton, is ab- 

 sorbed. The cartilaginous notochord gives way to a jointed 

 back-bone. A skull is developed ; numerous bones form in 

 the limbs, affording an attachment for the powerful muscles 

 which make the toad, and especially the frog, expert swim- 



