ORIGIN OF THE LAND VERTEBRATES 107 



of the Amphibian, such as a Frog, from the fish-like 

 Tadpole to the terrestrial air-breathing adult afford 

 a picture of how the change has taken place ; the 

 higher land Vertebrates, which never pass any of their 

 life in the water, have preserved in their develop- 

 ment the abbreviated history of their gill-possessing 

 ancestors ; and the Dipnoi, both in the nature of 

 their lungs and in their skull, betray their relation- 

 ship to the primitive group of fishes which gave origin 

 to the first land Vertebrates. 



