viii PREFACE 



character of Darwinian fitness, and at once 

 the whole difficulty was resolved. On all 

 sides instances of environmental fitness were 

 manifest, and casual search brought many 

 other cases to light. The forgotten literature 

 of natural theology is crammed with illustra- 

 tions, and the recent biological developments 

 of physical chemistry have provided still 

 others. It is, indeed, a very curious episode 

 in the history of thought that these well- 

 known facts should have been so long forgot- 

 ten or misconstrued. But, though forgotten, 

 they have, so to speak, lain dormant in the 

 minds of physical scientists, and I have found 

 both chemists and physicists ready to accept 

 them without hesitation. In the following 

 pages an attempt has been made to collect 

 and to interpret such facts, in so far as they 

 arise among the compounds of carbon, hydro- 

 gen, and oxygen, especially in the cases of 

 witer and carbonic acid. This restriction has 

 been adopted in order to facilitate the logical 

 discussion, and it should be borne in mind 

 that other phenomena, dependent upon the 

 properties of other substances, such as the 

 above-mentioned characteristics of phosphate 

 solutions, belong in the same category. 



The argument which has been thus devel- 

 oped is comparatively rigid and closely woven. 



