REGULATORY PROCESSES IN ORGANISMS PA ia 
is shown very clearly by the fact that isolation of a part from 
certain others during the course of reconstitution may alter the 
course of the process in the part, according to the degree and 
character of the isolation, 7. e., according to the correlative 
factors which are eliminated. By means of experiments of this 
kind it is possible even now to determine the action of various 
correlative factors in different stages of the process of reconsti- 
tution. 
5. The limits of reconstitution 
In every case the reconstitutional processes are limited and 
determined by existing conditions as the river is limited and 
defined by its banks and channel which its own activity has 
constructed in the environment through which it flows. It is not 
true without qualification that any part of certain organisms is 
capable of giving rise to any part. Driesch’s often repeated state- 
ment to this effect requires modification and limitation. The part 
is at most only provisionally capable of giving rise to any part; 
in other words, only when it constitutes a component of a system 
possessing certain characteristics, 7.e., only when it is subjected 
to or isolated from certain correlative factors. This is apparent 
from every recorded series of observations on reconstitution, except 
perhaps the most superficial. In some cases the system may con- 
sist of a single cell, in others of a large number of cells, but the 
fact remains the same. The power of reconstitution is limited, 
not unlimited. As I hope to show elsewhere for Planaria, and 
as I have shown for Tubularia (Child, ’07a, ’07b, ’O07c), the 
investigation of these limitations is of the greatest importance 
in throwing light upon the nature of the reconstitutional 
processes. When we find that the removal of a certain part, 
or even a certain amount of material, determines a different 
result from the removal of another part or a larger or smaller 
amount of material,,we are forced to the conclusion that the 
part or the material removed has some connection with the 
character, place or other factorsin the result, and furthermore, 
when we find that inhibition of the metabolic processes or 
certain of them in the part or the material is as effective in certain 
