76 CREATIVE EVOLUTION CHAP 



means, so it can physically determine the movements 

 of certain organisms ; ciliated Infusoria, for instance, 

 react to light. But no one would hold that the in- 



O 



fluence of light has physically caused the formation of 

 a nervous system, of a muscular system, of an osseous 

 system, all things which are continuous with the 

 apparatus of vision in vertebrate animals. The truth 

 is, when one speaks of the gradual formation of the eye, 

 and, still more, when one takes into account all that 

 is inseparably connected with it, one brings in some 

 thing entirely different from the direct action of light. 

 One implicitly attributes to organized matter a certain 

 capacity sui generis, the mysterious power of building 

 up very complicated machines to utilize the simple 

 excitation that it undergoes. 



But this is just what is claimed to be unnecessary. 

 Physics and chemistry are said to give us the key to 

 everything. Eimer s great work is instructive in this 

 respect. It is well known what persevering effort this 

 biologist has devoted to demonstrating that transforma 

 tion is brought about by the influence of the external on 

 the internal, continuously exerted in the same direction, 

 and not, as Darwin held, by accidental variations. His 

 theory rests on observations of the highest interest, of 

 which the starting-point was the study of the course 

 followed by the colour variation of the skin in certain 

 lizards. Before this, the already old experiments of 

 Dorfmeister had shown that the same chrysalis, accord 

 ing as it was submitted to cold or heat, gave rise 

 to very different butterflies, which had long been 

 regarded as independent species, Vanessa levana and 

 Vanessa prorsa : an intermediate temperature produces 

 an intermediate form. We might class with these 

 facts the important transformations observed in a little 



