72 CREATIVE EVOLUTION [chap. 



speaks of the gradual formation of the eye, and, still more, 

 when one takes into account all that is inseparably con- 

 nected with it, one brings in something 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 every- 

 thing. Eimer's great work is instructive in this respect. 

 It is well known what persevering effort this biologist 

 has devoted to demonstrating that transformation is 

 brought about by the influence of the external on the in- 

 ternal, 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 color variation of the skin in certain lizards. Before 

 this, the already old experiments of Dorfmeister had 

 shown that the same chrysalis, according as it was sub- 

 mitted to cold or heat, gave rise to very different butter- 

 flies, which had long been regarded as independent species, 

 Vanessa levana and Vanessa prorsa: an intermediate tem- 

 perature produces an intermediate form. We might class 

 with these facts the important transformations observed 

 in a little crustacean, Artemia salina, when the salt of 

 the water it lives in is increased or diminished. 1 In these 

 various experiments the external agent seems to act as a 

 cause of transformation. But what does the word " cause " 



1 It seems, from later observations, that the transformation of 

 Artemia is a more complex phenomenon than was first supposed. 

 See on this subject Samter and Heymons, "Die Variation bei Artemia 

 Salina" (Anhang zu den Abhandlungen der k. preussischen Akad. der 

 Wissenschaften, 1902). 



