Studies on Regulation. 471 



seen to attach and free themselves in the characteristic manner, 

 though here the muscular pi,ay of the margins is much less marked. 

 The piece as a whole adheres much less closely to the substratum, 

 however, than the normal animal. It is not at all difficult to 

 detach these pieces by means of a current of water from a pipette, 

 while the normal animal adheres so closely that detachment by 

 this method is often almost impossible. 



According to these observations pieces without the cephalic 

 ganglia show both a quantitative and qualitative difference from 

 normal animals as regards motor activities. All motor activities 

 appear to be less intense than under ordinary conditions and the 

 imperfect coordination in muscular movements alters the charac- 

 ter of the movements very greatly. 



In these pieces the margins of the head, apparently the chief 

 tactile organs, are of course absent and other parts of the body 

 are less sensitive than these. Reaction to tactile stimulation of 

 the lateral and other regions of the body is, however, less intense 

 and definite than in pieces containing the cephalic ganglia. The 

 eyes are also absent in these pieces and there is no marked re- 

 action to light, though in a few cases, I thought I could observe 

 some slight reaction (compare Parker and Burnett, '00). 



Individual differences in the behavior of pieces without ganglia 

 are often observed even where the cuts removing the head were at 

 the same level. Some pieces seem capable of more complete 

 coordination than others, as is clearly seen, for example, by the 

 rapidity with which they right themselves. These individual 

 differences are of most frequent occurrence when the cut is not 

 far from the ganglia and may be due to slight differences in level 

 of the cut, one piece retaining some parts of the nervous system 

 absent in others. Occasionally, however, they occur when the 

 cut was some distance posterior to the ganglia, and in such cases 

 must probably be ascribed to some structural or physiological 

 difference of which at present we know little. The fact of the 

 existence of such differences is however of interest as probably 

 indicating the existence of marked variations of some kind in the 

 nervous system. 



There seems to be some degree of correlation between size and 



