Degree of Injury and Rate of Regeneration 555 
chela of the double removal is slightly smaller on the average. 
The rates are 0.115 mm. and 0.113 mm. per day for the double 
and 0.115 mm. for the single removal. 
The individual variations in the present experiment are con- 
siderable. The differences between the two degrees of injury 
are so slight that they are probably not significant. No change 
in rate of regeneration with degree of injury is indicated in the 
individuals of the present experiment. 
DISCUSSION 
The various factors controlling growth and regeneration are 
so closely interrelated that no final analysis of any one can be 
expected until there is at least some understanding of all or 
nearly all of them. ‘This is nowhere more evident than in the 
case of the rate of regeneration. 
Nevertheless the data collected in the preceding experiments 
point conclusively to the general fact that the rate of regeneration 
of a part does not necessarily diminish with additional injury 
to the individual. On the contrary in the majority of the cases 
the rate of regeneration of a part is evidently higher when other 
parts of the animal have been removed at the same time than 
when the part alone has been removed. 
It is evident that the amount of injury involved in the removal 
of the part whose rate of regeneration is being compared as well 
as the amount of the additional injury must determine the char- 
acter of the result. The conclusive data in several experiments 
as well as the general mass of evidence obtained from all of them 
prove without question that within moderate degrees of injury 
a part regenerates more rapidly rather than less rapidly when 
it has regenerating company than when it regenerates by itself. 
The few exceptional cases showing a decrease in rate are capable 
of explanation on the grounds either of an incomplete control of 
subsidiary factors or of the presence of too high a degree of injury. 
The strength of the statement is made still stronger if possible 
by the consideration that additional injury to an individual 
involves a whole train of consequences likely to lead to disturb- 
