Studies on Regulation. 473 



ducting paths. This being the case we should expect to find less 

 power of reaction to stimuli, less complexity and a lower degree of 

 correlation in the movements. These are exactly the conditions 

 that we do find. 



It is, I think, desirable to avoid the use of the word "sponta- 

 neous" in this connection since the difference between sponta- 

 neous and non-spontaneous movements seems to be merely one 

 of degree of complexity and correlation or coordination. Re- 

 moval of the principal paths by which stimuli enter and a part of 

 the structures which connect these paths with other parts oi the 

 nervous system must reduce the complexity of structure and con- 

 sequently of the visible activities dependent upon this structure. 



Among these observations the most important point for the 

 present consideration is the presence of the power of progressive 

 locomotion in some degree in pieces deprived of the ganglia. 



Loeb ('94, '99) found that in the case of Thysanozoon loss of 

 the power of progressive locomotion resulted from the removal of 

 the cephalic ganglion. This is certainly not the case in Lepto- 

 playia, and indeed experiments of my own upon Thysanozoon led 

 me to the conclusion that even here the pieces without the ganglia 

 still possessed some slight power of locomotion, though much less 

 than that of the normal animal. In both Thysanozoon and Lepto- 

 plana these pieces are capable of righting themselves after being 

 turned over, but the change in position is much less rapid than in 

 normal animals and frequently is accomplished only after re- 

 peated attempts, or in some cases does not succeed at all, and the 

 piece gradually becomes quiet. 



One other point of considerable interest must be considered. 

 In Leptoplana I observed a marked difference in the power of 

 locomotion and of coordination in general in pieces cut at different 

 levels, the activity decreasing as the portion of the body removed 

 with the cephalic ganglia increased. If, for instance, an individual 

 was cut transversely two or three millimeters posterior to the 

 ganglia the posterior piece was much more active and was capable 

 of more rapid locomotion and more perfect coordination than a 

 posterior piece obtained by a cut posterior to the middle of the 

 body. In general the greater the distance between the cut and 



