THE EVOLUTION OF MAN 



there is once more a living form which gives a 

 direct clue. In a few small rivers of the eastern 

 part of the Australian continent, a creature has 

 been found which externally, so far as scales, fins 

 and gills are concerned, resembles a large salmon 

 or carp. But if we study its internal structure 

 we find that it has also perfectly developed, 

 serviceable lungs, and if we study its mode of liv- 

 ing the logical purpose of this double supply of 

 breathing organs becomes plain. During the 

 dry season the little rivers of this region dry out 

 almost completely. Nothing remains of them 

 but a few pools of bad, brackish water in which 

 the fishes are crowded together and encroach on 

 one another's supply of air. Under these trying 

 conditions, this strange animal swims to the sur- 

 face of the water, draws air into its lungs and 

 thus breathes after the manner of a genuine land 

 animal, which dispenses altogether with water 

 for breathing purposes. 



This paradoxical fellow who can change him- 

 self at will into a fish and into a newt, has been 

 called the "newt-fish," and its Latin name is 

 Ceratodus. But this name was originally in- 

 vented for the purpose of applying it to a band 

 of fishlike creatures, which may be traced by fossil 

 remains throughout a long evolution far back into 



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