June, 1919] 



Fauna of Rock Bottom Ponds 



459 



All of the species in this pond were also to be found in ponds 

 on the mainland. There were no peculiarly island types. For 

 most of the inhabitants in isolated ponds such as these in this 

 series a few miles of water are probably no more of a barrier 

 than as many miles of land. In fact it may be less of a barrier 

 since it is an inhabitable medium. 



TABLE 19. 



The catfishes were the only inhabitants that would have had 

 to be introduced by human agency. The turtles were also prob- 

 ably introduced in this way but there is a possibility of their 

 having migrated from the lake. Assuming that other fishes 

 had been thrown into the pond, on which point I have no data, 

 catfish were apparently the only fish that contrived to survive. 

 Their young were numerous. Two physical factors probably 

 operated against the survival of other fishes : (a) the quantity of 

 silt, more or less constantly kept suspended in the water by the 

 cattle ; and (b) the foulness of the water also due to the cattle. 



