THE TRANSITION TO LAND 



381 



R. Marlin Perkins, Chicago Park District 



Fig. 26.2. A tiger salamander, Ambystoma tigrum. 



was the cause of the failure of the axolotl to metamorphose. The ad- 

 dition of a little iodine to the water of an aquarium or, better still, the 

 feeding of fresh thyroid glands to the axolotls causes them to become 

 land salamanders even though they stay in Colorado. 



Strange to say, salamanders have internal fertilization even though 

 they have no organs for copulation. The male and female first go 

 through a courtship "dance" in the water, then the male deposits packets 



.fc \f*Si 





Photo by Winchester 



Fig. 26.3. A toad. From this photograph it is easy to see where we got the expres- 

 sion "puffed up like a toad." The warty skin also shows where we got the superstition 

 that handling toads would cause warts on the hands. 



