The Problem of Adaptation 29 



living in the water might not be killed, which would be the 

 case if the ice sank to the bottom, but such a method of 

 interpreting physical phenomena would scarcely commend 

 itself to a physicist. 



The formation of a covering of oxide over the surface of 

 a piece of iron delays the further process of oxidation, but 

 who will imagine that this property of iron has been ac- 

 quired in order to prevent the iron from being destroyed by 

 oxygen ? 



If a piece is broken from a crystal, and the crystal is 

 suspended in a saturated solution of the same substance, 

 new material is deposited over its whole surface, and, as it 

 grows larger, the broken side is completed and the crystal 

 assumes its characteristic form. But of what advantage is 

 it to the crystal whether it is complete or incomplete? In 

 the case of an animal it is of some importance to be able 

 to complete itself after injury, because it can then better 

 obtain the food necessary to keep it alive, or it can better 

 escape its enemies ; but this is not the case with the crystal. 



In conclusion, therefore, it is obvious that the adaptations 

 of organisms are something peculiar to living things, and 

 their obvious purpose is to maintain the integrity of the indi- 

 vidual, or that of the species to which the individual 

 belongs. We are, therefore, confronted with the question 

 as to how this peculiarity has come to be associated with 

 the material out of which living things are made. In sub- 

 sequent chapters this will be fully discussed, but before we 

 take up this topic, it will be necessary to reach some under- 

 standing in regard to the theory of evolution, for the whole 

 subsequent issue will turn upon the question of the origin of 

 the forms of animals and plants living at the present time. 



