The Living Machine 



309 



the wind, fall on the leaf, there is no movement of the ten- 

 tacles or secretion of digestive fluid, but should an unlucky 

 insect alight on a sun dew leaf attracted by the honey-like 

 drops upon the tentacles, they bend over and figuratively 

 speaking seize upon the intruder, while the edges of the leaf 

 fold together, thus wrapping the leaf about its body. The 

 digestive glands complete the tragedy and what was once an 

 insect now becomes incorporated in a leaf. Here we find a 

 relatively complex series of reactions co-ordinated, or working 

 in harmony, in an organism lacking any special nervous or 

 co-ordinating system altogether. 



SUN DEW LEAF 



Showing sticky hairs and entrapped insect. From Needham and 

 Lloyd, ''The Life of Inland Waters," Comstock Publishing Company. 



Can these responses of the unicellular animals and plants be 

 explained on a physico-chemical basis? This the leader of 

 the mechanist school in America, Jacques Loeb, endeavors 

 to do with his "forced movement" or "tropism theory." 

 According to this theory every organism is in a state of 

 physiological equilibrium or balance with respect to a median 

 plane of symmetry, until it is subjected on one side or the 

 other to a stimulus, such as heat, light, electricity, etc.; 

 which stimulus induces certain physico-chemical changes, 

 differing in degree on either side of the body, this difference 

 forcing the organism to respond unequally on the two sides, 

 and then perform a "forced movement" or a "tropism" 

 (turning). While a great many of the one-celled organisms 



