218 Herbert W. Rand 
These reparative responses, then, are potentially of local char- 
acter. They are not necessarily dependent upon the organism 
as a whole individual, but they may be initiated and carried out 
by the tentacle tissues in the near vicinity of the plane of cutting. 
We have here a very clear instance of a noteworthy peculiarity 
of organisms in general, namely, a purely local response to change 
of conditions—a response effected entirely independently of any 
immediate action of the organism as a whole—and yet one which 
is admirably adapted to the needs of the whole organism. It can 
hardly be imagined that the repair of the distal cut end is of any 
advantage to the detached tentacle, for the proximal cut end (in 
Condylactis) is not readily repaired and the fragment of tentacle 
under ordinary conditions is capable of maintaining life for only 
a few days at the most. In the light of regeneration experiments 
on the lower invertebrates it would seem fairly certain that even 
under more favorable conditions there could be no regeneration 
from the fragment of tentacle. Yet it is certainly true that the 
closing of the cut end of the fragment tends toward the independent 
existence of the fragment. If it were to continue to live indef- 
nitely the closing or healing of the cut ends would be the thing of 
primary importance for it. The behavior of fragments of ten- 
tacles might be described as an attempt, albeit an ineffectual 
one, to survive. Certainly not, in a narrow sense, an “attempt”’ 
having origin in the particular individual of my experiment, but, 
in a broader sense, an expression of those fundamental and dis- 
tinctive properties of living substance which tend toward persist- 
ence and increase of organisms. 
The survival of actively motile fragments of Aiptasia tenta- 
cles for a week or more (see p. 228) suggests the possibility that 
under more favorable conditions of experimentation than | was 
able to arrange with the time and means at my disposal the life 
of such fragments might be prolonged indefinitely. Indeed, is 
it not conceivably possible that by use of a suitable nutrient me- 
dium and by chemical stimulation growth activities might be aroused 
in such fragments and regeneration of some sort induced? So 
far, too, as the utility of reparation to the fragment itself is con- 
cerned, it is possible to regard the matter in either a retrospective 
