Studies on Regulation. 489 



so far as I can see, in the frequency of muscular contraction and 

 the consequent internal pressure upon the regions adjoining the 

 cut; it is possible that more frequent contraction and movement 

 might force the tissues out through the wound more rapidly, 

 though this is not a factor of great importance in any case. 



In the cases under consideration at present I think we may 

 regard the new tissue present two weeks after section as repre- 

 senting to a large extent this first stage. At this time the new 

 parts are functional in movement to only a very slight degree and 

 may be regarded as practically undifferentiated outgrowths. It 

 is possible that the slightly greater amount of this tissue in the 

 pieces with ganglia may be due to the more frequent movements 

 which have so to speak forced more material out through the 

 wound, or it may be that we have here the beginnings of the differ- 

 ence which is more marked in later stages. In earlier stages than 

 those figured the differences were, as might be expected, even less 

 marked. 



For the purpose of analysis we may consider the stage of differ- 

 entiation as following the first indifferent stage which we have 

 considered. As a matter of fact the two overlap in varying 

 degree and manner according to circumstances. The fate of the 

 new material must be regarded as depending essentially upon its 

 relations to the old parts, or in the words of Driesch, its fate is a 

 function of its position, since these relations determine what 

 stimuli it receives and to what conditions external and internal, 

 it is subjected. Under ordinary circumstances the new part 

 supplies functionally the place of the part removed though very 

 imperfectly at first; or, in other words, the animal or piece attempts 

 to use it as it would use the part removed if this were present. 

 I am inclined to believe that this "attempt at use" is an important 

 factor if not the most important in determining what the new part 

 shall become. But from the time when the use of the part begins, 

 or let us say, when functional stimuli reach it, it is subjected to 

 conditions differing widely from those of the first stage. By these 

 conditions the "indifferent" material is moulded into its definitive 

 form and structure. The influence of the conditions connected 

 with locomotion on the form of regenerating posterior regions has 



