Those familiar with the theories of evolution know the extensive rôle ascribed to the adaptations of organisms. The writer in 1889 called attention to the fact that reactions to light--_e. g._, positive heliotropism--are found in organisms that never by any chance make use of them; and later that a great many organisms show definite instinctive reactions towards a galvanic current--galvanotropism--although no organism has ever had or ever will have a chance to be exposed to such a current except in laboratory experiments. This throws a different light upon the seemingly purposeful character of animal reactions. Heliotropism depends primarily upon the presence of photosensitive substances 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 environment 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. Cuénot speaks of "preadaptation" 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: (1) the phenomena of vital creation or organizing 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.
These introductory remarks may perhaps make it easier for the reader to retain the thread of the main ideas in the details of experiments and tables given in this book.
THE SPECIFIC DIFFERENCE BETWEEN LIVING AND DEAD MATTER AND THE QUESTION OF THE ORIGIN OF LIFE