476 C. M. Child. 



chief sense organs, z. e., the paths by which more or less definitely 

 localized stimuli enter the nervous system, is the primary factor 

 in their predominance. 



With regard to the existence of "centers" in the nervous system 

 I agree essentially M^ith Loeb ('99) and I think the relations above 

 described support this view. Coordinated movements are the 

 result of series of interrelations and exist after mutilation in the 

 degree in which the interrelations remain intact or are reestab- 

 lished. 



The case of Leptoplaria as cited affords strong support to the 

 view that the difference between "spontaneous" and "non- 

 spontaneous" motor-activity is simply one of degree. Moreover, 

 it is impossible to say that one part of the central nervous system 

 in Leptoplana is necessarily connected with coordinated move- 

 ment while another is not. It is rather the amount of nervous 

 tissue — in all probability the completeness of the system of con- 

 nections of parts — than the presence of any one portion which 

 determines the results. 



2. The Relation Between the Central Nervous System and 

 Posterior Regeneration. 



From Schultz's ('02) account of regeneration in Leptoplana 

 atomata, it is evident that there is but little difference as regards 

 regeneration between this species and L. tremellaris, but in the only 

 case in which Schultz and I are really concerned with the same 

 problem our interpretations of the facts differ widely. 



As regards the limits of regeneration in Leptoplana a brief 

 preliminary statement will suffice here. Posterior regeneration 

 from a cut surface is qualitatively complete at all levels posterior 

 to the cephalic ganglia whether these are present or not and an- 

 terior regeneration is complete only when the ganglia are present 

 at least in large part, /. e., only anterior to them. In other words, 

 regeneration of a head is impossible in the absence of the cephalic 

 ganglia but posterior regeneration occurs whether they are present 

 or not. In the absence of food the size of the new part is never as 

 great as that of the part removed, but this is not of great impor- 

 tance. 



