MYSTERIES OF LIFE AND MIND 



effect of the light, the moth will go round and 

 round as planets spin about the sun, or, in other 

 cases, describe a curious zigzag motion, something 

 like a comet. There is naught here but the play of 

 physical forces. 



More curious still is the effect of mere contact. 

 If you turn over a starfish, it quickly rights itself. 

 This seems a highly sensible thing to do. Still, as 

 Dr. Loeb found, if you suspend the starfish in water, 

 attaching its arms to bits of cork, it keeps turning 

 over and over, with no seeming preference for 

 which side is up. If a piece of wood or stone be 

 offered, to which it may cling, no matter what be 

 the position, it seems satisfied. Unless its feet 

 have something solid to cling to, the nerves are 

 apparently stimulated ; hence the turning motions. 

 Contact brings the animal to rest. This is what 

 Dr. Loeb calls stereo tropism. Long words like 

 these seem merely like substituting one mystery 

 for another, but they describe actions as simple 

 as the words are hard. 



Physiologists who had a bent for philosophy were 

 not slow to see the drift of all this ingenious and 

 disturbing work. If the forces that shape the ex- 

 quisite forms assumed by the crystals on a frosty 

 window-pane, or the leaves and branches of a tree, 

 are the same as those which guide a moth in its 

 flight, there seems no good reason for stopping here. 



203 



