316 C. M. CHILD 



interest in this connection: the experiments show that even m 

 the case of organs of such definite form and localization m the 

 body as are the eyes, the position, form and nmnber of the 

 organs may be dependent upon dynamic conditions in the system 

 as a whole, rather than upon any specific or .localized hereditary 

 element. 



In general I think we may say that so far as these experiments 

 go they indicate that what is inherited is merely capacity for 

 reaction, and that such capacity consists in the constitution and 

 the correlation of parts of the reproductive system or element. 

 The same 'character' may in one case be chiefly the result of 

 constitution of a locaUzed part, in another it may be largely the 

 result of correlation between different parts. But in the cases 

 of constitutional inheritance there is good reason to believe that 

 correlation with other parts in the past has played an important 

 part in bringing about the particular constitution concerned. 

 That is to say, this constitutional factor in inheritance cannot be 

 regarded as in any sense the fundamental factor, in other words, 

 we cannot regard the reproductive element as originally a mosaic 

 of localized hereditary qualities. In all cases where it approaches 

 this form, there is reaason to believe that the existing specifica- 

 tion is the result of a specification or differentiation which has 

 already taken place and in which both constitution of parts and 

 correlation between them have played a role. In more general 

 terms, the reproductive element may be in very different stages 

 of development at the time when it is isolated from the parent 

 organism. 



The experiments show that any piece of Planaria capable of 

 development into a whole, or into anything with definitely 

 localized parts is not an equipotential system. I do not believe 

 that any reproductive element which is capable of development 

 is such a system: organization, i.e., different constitution of 

 different parts and physiologic correlation between them to a 

 greater or less extent, is necessary for development. 



These conclusions and suggestions apply primarily to inherit- 

 ance in the pieces of the planarian body, but it seems probable 

 that there is no very fundamental difference between such a 



