220 Herbert W. Rand 
cut end of an attached tentacle are under nervous control, and it 
may be that the nerve mechanism of the entire actinian partici- 
pates in that control. Even if that be true, we may well suppose 
that the fragment of tentacle exhibits the same kind of muscular 
activity by virtue of possessing the same kind of nerve mechanism, 
although in less quantity. 
This reparative behavior of excised tentacles calls to mind the 
observation of Parker (’96) on excised tentacles of Metridium. 
He stimulated excised tentacles with meat juice and found that 
they bend in a direction corresponding to the original position of 
the mouth in relation to the tentacle. Thus, it appears that “each 
tentacle has within itself a complete and independent nervous 
and muscular mechanism capable of carrying out normal re- 
sponses” (p. 112). However, in the responses both to cutting 
and to stimulation by food we see, coexistent with a high degree of 
autonomy in the tentacle, a certain necessary relation of it to the 
whole organism. This relation continues to be expressed even 
after the tentacle is separated from the rest ofthe animal. In 
such behavior of a fragment the zdea of the whole is expressed, 
although in much less detail, yet quite as vividly as if the frag- 
ment had regenerated the whole actinian. Whatever may be the 
nature of the mechanisms underlying these, in a sense autonomous, 
responses which are carried out by fragments of animals, can we 
avoid the conception that somewhere in the total life-history—in 
ontogeny or phylogeny—the indwiduality or totality of the organ- 
ism or some “original principle of unity” (Lillie, ’06) has been a 
cause operative, in a way which is beyond our knowledge, toward 
the establishment of such mechanisms and the relations which 
their activities express ? 
Turning now to the second phase of the reparation process, 
namely, the slow structural readjustment by which the cut end is 
permanently closed, I believe that we have here to deal with a 
very fundamental and primitive property of the tissues concerned. 
In the Metazoa in general the early ontogeny includes a two- 
layered condition. Of these two layers the ectoderm gives rise 
to the definitive outer layer of the body, while the chief derivative 
of the entoderm is the enteric tube. Experiments which have 
