304 C. M. CHILD 



aria in which the course of regulation has been different attain 

 identical results. To call such regulatory processes equifinal is 

 simply to beg the whole question. Certainly the general morpho- 

 logical similarity affords no adequate g-rounds for such conclu- 

 sions. We have much more reason to believe that the results 

 are not alike in any two pieces of Planaria, and I hope to show in 

 later papers that they actually are different in at least certain 

 cases where "wholes" are formed. 



The visible morphological structure of the organism is, so to 

 speak, merely a very incomplete record of the dynamic processes. 

 Only the most characteristic, the least variable, the most endur- 

 ing or the most intense leave records sufficiently well marked to 

 appear as visible structure. Two organisms may be indistin- 

 guishable or almost indistinguishable as regards their general 

 form and structure and still be widely different from each other 

 in many respects. 



And again, the distinction between wholeness and incomplete- 

 ness is likely to lead us astray in another direction. It becomes 

 easy to regard the formation of a whole from a piece as ' success ' 

 and the formation of a partial structure as 'failure'. But when 

 we do not impose such notions upon nature as rigid categories we 

 must recognize the fact that success and failure are not involved. 

 Every living system is as much a success as any other. It is 

 simply the product of a certain constellation of conditions, internal 

 and external. 



In the investigation of the regulations of form and structure in 

 organisms the stress has too often been laid upon wholeness to 

 the more or less complete exclusion of other results. It is often 

 said that any piece, or almost any piece from the body of Plan- 

 aria produces a new whole. How far this is from being true the 

 above described experiments show. Strictly speaking, the limits 

 of wholeness in the regulation of this form are very narrowly re- 

 stricted. So far as our experiments go at present, the formation 

 of a 'whole' in Planaria is possible only in pieces above a certain 

 size which varies with the region of the body and with various 

 external conditions. Manifestly this process of formation of a 

 whole is immediately dependent upon the kind and the rate of 



