28 Evolution and Adaptation 



parts of the body mainly in that they are made of different 

 compounds having different properties, as the above com- 

 parisons have shown. But the regulations of the machine 

 have been added to it by man on account of their useful- 

 ness to himself, and are not properties of the material of 

 which the machine itself is composed. This shows, I think, 

 the inappropriateness of making any comparison between 

 these two entirely different things. 



If, then, we find the comparison between machines and 

 organisms unprofitable, can we find any other things in 

 inorganic nature that can be better compared with the 

 phenomenon of adaptation of the organism ? The following 

 phenomena have been made the subject of comparison from 

 time to time. The bendings, which are gradually made by 

 rivers often lead to a meeting of the loops, so that a direct, 

 new communication is established, and the course of the 

 river is straightened out. The water takes, therefore, a 

 more direct course to the sea. It cannot be said, however, 

 to be of any advantage to the river to straighten its course. 

 Again, a glacier moulds itself to its bed, and gradually 

 moves around obstacles to a lower level, but this adaptation 

 of the glacier to the form of its surroundings cannot be 

 said to be of advantage to the glacier. On the contrary, 

 the glacier reaches so much the sooner a lower level where 

 it is melted. 



The unusual case of a solid being lighter than the liquid 

 from which it forms, as seen in the case of ice, has been 

 looked upon as a useful arrangement, since were the reverse 

 the case all rivers and ponds would become solid in winter 

 in cold climates, and the polar regions would become one 

 solid block of ice. But no one will suppose for a moment 

 that there is any relation between the anomalous condition 

 of the lightness of ice, and its relation to the winter freezing 

 of streams, ponds, etc. It has even been suggested that this 

 property of ice was given to it in order that the animals 



