Behavior and Form 169 



In experiments on Planaria Child has shown that 

 the head and pharynx do not attain their normal 

 shape and structure when movement is largely in- 

 hibited by anaesthetics, but he does not conclude that 

 movement is the only factor involved. Regenera- 

 tion and all other modes of the regulation of or- 

 ganic form he regards as the outcome of functional 

 regulation. Movement plays a certain role in shap- 

 ing the outline of some organisms, especially those 

 with physically plastic tissues, but "it is merely one 

 of a great variety of functional factors." 



While studying the regeneration of the infuso- 

 rian Loxophyllum I found that I was dealing with 

 an organism in which regeneration and behavior are 

 apparently closely connected. Loxophyllum is a 

 flattened infusorian that moves by gliding on the 

 bottom on its right side. It confines its activities 

 usually to a small area for a considerable time; first 

 it glides forward a short distance, then reverses 

 its cilia and swims backwards, turns toward the 

 oral side and then swims forward again in a new 

 direction. As the animal swims forward the body 

 is elongated, but as it goes backward the body is 

 invariably shortened and widened, thus showing a 

 constant association between the direction of the 

 beat of the cilia and the contraction of the myo- 

 nemes. In the changes in the form of the body it 

 is the contraction and extension of the oral side 

 that play the most important part, and it is along 

 the oral side that the myonemes are especially 



