22 CELL, INTELLIGENCE THE CAUSE OF EVOLUTION 



from what you or I would do under the same circum- 

 stances. Then he makes the following comment : "In 

 certain animals, for instance in daphnia and in certain 

 marine copepods, a decrease in temperature also increases 

 the tendency to positive heliotropism. If the mere addi- 

 tion of acid is not sufficient to make daphnia positively 

 heliotropic, this may often be accomplished by simultan- 

 eously reducing the temperature." In other words, he 

 might as well say that if you cannot start them moving 

 by burning them with acid you can do so by freezing or 

 making it uncomfortably cold for them. Why should 

 they not try to escape from a place where they are freez- 

 ing or where their skin is being irritated and eaten by 

 acid? 



I will quote you one more of his illustrations, which he 

 thinks is very significant of the fact that some animals 

 become at times possessed by a property that he calls 

 heliotropism. I think it is the most absurd illustration of 

 them all. Here is what he has to say about the young 

 beetle, who comes out of the ground in the spring hungry 

 and is very much in need of something to eat : "This 

 change in the heliotropic sensitiveness produced by cer- 

 tain metabolic products in the animal body is of great 

 biological significance. I pointed out in former papers 

 that it serves to save the lives of the above mentioned 

 young larvae of chrysorrhoea. When the young larvae are 

 awakened from their winter sleep by the sunshine of the 

 Spring, they are positively heliotropic. Their positive 

 heliotropism leaves them no freedom of movement but 

 forces them to creep straight upward to the top of a tree 

 or branch. Here they find the first buds. In this way 

 their heliotropism guides them to their food. Should 

 they now remain positively heliotropic they would be held 

 fast on the ends of the twigs and would starve to death. 



