299 Herbert W. Rand 
Finally, then, in the reparation of these actinian tentacles [| 
believe that we may distinguish two totally different phenomena. 
The structural closing of the wound is due, not to any special proc- 
ess peculiar to actinians but, upon the contrary, to certain funda- 
mental properties of the elements of the two primary body layers 
of Metazoa—properties to which these organisms must owe their 
very origin and existence. In the other phenomenon, the tem- 
porary muscular control of the wound, we see a much narrower 
and more highly specialized kind of activity. In just this par- 
ticular method of operation it is perhaps peculiar to the actinians. 
It is very clearly an adaptation to the circumstances that wounds 
are necessarily of large area as compared to the thickness of the 
body layers and that to await the closing of such wounds by the 
slow primitive process of cell-rearrangement would involve delay 
more or less disadvantageous if not positively dangerous to the 
organism. 
The fact that the fragment of tentacle repairs itself in the same 
way that the attached tentacle does is not necessarily significant 
of any peculiar autonomy of the structural units of an organism. 
It results from two conditions; first, that the fragment includes both 
body layers with their distinctive and ever inherent primitive 
properties; and secondly, that the peculiar actinian features of 
organization in general—more particularly in this connection the 
nerve-muscle arrangement—do not involve sharp localization of 
tissues into spatially restricted organs, but rather a diffuse distri- 
bution of the more specialized structures and their corresponding 
functions. 
Finally, if we compare the actinian tentacle with similar ccelen- 
terate structures—the tubularian stem and Hydra—upon the one 
hand, and with the earthworm upon the other, it may be observed 
that the actinian tentacle possesses a somewhat greater complexity 
of structure than the tubularian stem or Hydra, correlated with 
its greater size. ‘This greater complexity is seen chiefly in the 
differentiation of definite systems of muscle fibers. Correspond- 
ing to this particular additional complexity of structure we find in 
the actinian tentacle a feature of behavior, namely, the provisional 
muscular control of the wound, which is superadded to the be- 
