28 



The Mechanistic Conception of Life 



In a series of experiments I have shown that the heUotropic 

 reactions of animals are identical with the heliotropic reactions 

 of plants. It was knoTNTi that sessile heliotropic plants bend 



Fig. 18 



Fig. 19 



Figs. 18 and 19. — Positive heliotropism of the polyps of Eudendrium. The 

 new polyp-bearing stems all grow in the direction of the rays of light which is 

 indicated by an arrow in each figiire. (From nature.) These animals bend in 

 the same way to the light as the stems of positively heliotropic plants kept imder 

 siniilar conditions, 



their stems to the source of light until the axis of symmetry of 

 their tip is in the direction of the rays of light. I found the 

 same phenomenon in sessile animals, e.g., certain hydroids 

 and worms. Motile plant organs, e.g., the swarm spores of 

 plants, move to the source of light (or if they are negatively 



