218 C. M. CHILD 
respects as the removal of the part or the material, we have at- 
tained a basis for investigation and analysis which is proof against 
such assumptions as those which Driesch has made, e. g., concern- 
ing the nature of the ‘harmonious-equipotential system.’ For 
Driesch the limitations of the reconstitutional processes appear 
to be of secondary importance, but I believe that any one who 
will investigate and analyze these limitations at all thoroughly 
will find that they are not only essential features of the regulatory 
processes, but that they afford us one of the best means of gaining 
some insight into their nature. As water does aot constitute a 
river, except under certain limiting conditions, so certain sub- 
stances or processes do not constitute an organism or even life 
except under certain limitations. The water contains the poten- 
tialities for giving rise to any kind of a river, as well as other 
specific ‘machines,’ but none of these exist until thespecific limita- 
tions are present. The case is essentially similar as regards the 
organism. The specific ‘machine’ exists only so far as the limita- 
tions exist. And the investigation of the limitations of reconsti- 
tution affords at present one of the best methods, if not the best, 
for demonstrating this to be a fact. 
REPRODUCTION IN GENERAL AS A FORM OF RECONSTITUTION 
In another paper (Child, ’11a) I have discussed at length the 
significance of physiological isolation of parts as a factor in repro- 
duction. I have shown that certain degrees and kinds of physiolog- 
ical isolation of parts may arise as the result, first, of an increase in 
size; second, of decrease in correlative control or physiological 
dominance of a part in consequence of decreased activity in it; 
third, of decreased conductivity or transmissibility of correlative 
processes, agents or conditions; fourth, of decreased receptivity, 
sensitiveness or irritability of certain parts to the correlative factors 
originating in other parts. Furthermore, we know from experi- 
ment, as I have shown, that in a considerable number of cases 
physiological isolation of parts serves as well as physical isolation 
by section to bring about reconstitution; and if it were possible 
to perform the experiment, it is practically certain that we should 
find the same to be true for many other cases. 
