No. 554 ] - 1 DAPTA HON IN LI VING AND NON-LIVING 7 3 



case, the statement of the realization implies the poten- 

 tiality, for an object is obviously adapted to doing and 

 being what it does and is. 



However, doing and being are only relative, for any 

 object may change its state more or less effectively and 

 may possess attributes in different degrees, and our in- 

 terest in realized potentialities lies not in the fact, bnt in 

 the degree of adaptation. Furthermore, the degree of 

 adaptation depends clearly upon the extent to which the 

 object considered possesses those properties or qualities 

 about which our idea of adaptation centers, and so atten- 

 tion is at once turned to the properties or qualities as 

 such. 



I may draw an illustration of actually observed adap- 

 tations from the science of geology, which perhaps in- 

 terests itself as much in the survival and distribution of 

 rock masses as does biology in the survival and distribu- 

 tion of living things. My example has to do with the nat- 

 ural selection and distribution of certain boulders and 

 pebbles in a deep Californian valley. 



At the time of the filling of the Salton sink by the un- 

 ruly Colorado River, the only loose stones of the inun- 

 dated area that were able to keep themselves in contact 

 with the air were fragments of pumice. These were 

 adapted to float upon water, and they largely refused to 

 be submerged. With the rising waters they also rose, and 

 thus were able to take advantage of air movements to re- 

 distribute themselves. Had it not been for the floating 

 adaptation, these pumice pebbles would have suffered 

 temporary extinction in the form of submergence, and 

 they would not have been able to survive and to gain 

 dominance in the pebble population of certain Salton 

 beaches which they forthwith proceeded to invade. We 

 have reason to believe that this sort of spontaneous mi- 

 gration of pumice pebbles has taken place many times 

 before in the Salton valley, at periods and seasons when 

 edaphic and climatic conditions happened to favor such 

 readjustments of the tension lines, and that the present 



