12 Introductory Remarks 



throws a different light upon the seemingly purposeful 

 character of animal reactions. Heliotropism depends 

 primarily upon the presence of photosensitive sub- 

 stances in the eye or the epidermis of the organism, 

 and these substances are inherited regardless of whether 

 they are useful or not. It is only a metaphor to call 

 reactions resulting from the presence of photosensitive 

 substances ' ' adaptation. ' ' In this book other examples 

 are given which show that authors have too often 

 spoken of adaptation to environment where the en- 

 vironment was not responsible for the phenomena. 

 The blindness of cave animals and the resistance of 

 certain marine animals to higher concentrations of sea 

 water are such cases. Cuenot speaks of "preadapta- 

 tion" to express this relation. The fact is that the 

 *' adaptations" often existed before the animal was 

 exposed to surroundings where they were of use. This 

 relieves us also of the necessity of postulating the 

 existence of the inheritance of acquired characters, 

 although it is quite possible that the future may furnish 

 proof that such a mode of inheritance exists. 



6. We have mentioned that according to Claude 

 Bernard two groups of phenomena occur in the living 

 organism: (i) the phenomena of vital creation or or- 

 ganizing synthesis (especially in the egg and during 

 development) ; (2) the phenomena of death or organic 

 destruction. These two processes are briefly discussed 

 in the first and last chapters. 



