Studies on Regulation. 539 



when less than half the ganglionic tissue remains their behavior 

 approaches that of pieces without ganglia. Moreover, if after 

 removal of the ganglia by a transverse cut the body be split longi- 

 tudinally or near the median plane the two halves show similar 

 activity which is not very different from that before their separa- 

 tion; if, however, the plane of section lies far to one side of the 

 median plane the smaller piece shows scarcely any motor activity, 

 while the longer retains the characteristic activity of a piece with- 

 out ganglia. These differences are of course, due to the nervous 

 system. When the plane of section lies near the median plane 

 each half contains the nervous structures of that half of the body, 

 but as the plane of section approaches the lateral margin the 

 smaller pieces contain less and less of the nervous system until in 

 the extreme lateral region nothing remains in them but some of 

 the peripheral nerves. Probably closer observation would show 

 rapid changes in motor activity according as the plane of section 

 passed on one side or the other of one of the nerve cords, but I 

 I have not paid especial attention to this point. 



Comparison of this description of the motor activity of longi- 

 tudinally cut specimens with the statements regarding lateral 

 regeneration renders it clear at once that the same parallelism 

 between motor activity and regeneration exists as in the cases 

 already discussed, so that nothing is to be gained by going over 

 the whole series of experiments upon lateral regeneration. I shall 

 describe only a few cases by way of illustration, calling attention 

 to certain points of especial interest. 



Cases of the removal of less than half the body by longitudinal 

 section from end to end need not detain us since in all cases the 

 amount and rapidity of regeneration vary with the size of the part 

 removed, /. e., the larger the part removed the more rapid the 

 regeneration, so that regeneration of a large part does not require 

 much more time than regeneration of a small part. These 

 relations are similar to those described for posterior regeneration 

 from levels posterior to the ganglia and for anterior regeneration 

 in the presence of the ganglia, and are to be interpreted in the 

 same manner as due to the role which the new tissue is required 

 to play in functional — doubtless chiefly motor activity. 



