170 STUDIES IN GENERAL PHYSIOLOGY 
is opened at both ends. The meat after being swallowed 
was often ejected undigested. Actual nutrition of these 
animals was, of course, impossible. 
5. We have thus far considered only the head piece of a 
divided Actinian. The foot piece which possesses an 
uninjured foot at its aboral end, and a cut edge at its oral 
end, soon regenerates tentacles at this end and a normal 
mouth is formed. But even before the tentacles and mouth 
have begun to regenerate, the oral opening assumes the 
functions of a mouth. Pieces of meat are taken up and 
swallowed, while I have never seen it take up wads of paper 
or grains of sand. 
6. While the entire body of Cerianthus, with the excep- 
tion of the oral plate, is endowed with contact-irritability, 
this contact-irritability is confined to the basal surface of the 
body of Actinia equina. By means of this surface the ani- 
mal attaches itself to solid bodies. The surface of the foot 
has here the same function as the roots of Tubularia, only 
with this difference, that through (spontaneous) internal 
changes the Actinian can again leave the surface of the body 
to which it is attached, while this is not possible in Tubu- 
laria. It is interesting to note that the nature of the sur- 
Face of the solid body ts not a matter of indifference in call- 
ing forth these reactions. When no other object was near, the 
animal attached itself to the glass wall of the aquarium and 
slid about upon it; when, however, I placed the shell of a 
Mytilus in the aquarium, and the animal came in contact 
with it in the course of its movements, it immediately 
attached itself to it and remained there, it mattered not 
whether the shell was empty or occupied. 
The surface of an ulva leaf in the aquarium acted in the 
same way as the surface of the mussel. While the animal 
would always leave the glass to which it was fastened, to 
attach itself to an ulva leaf when brought in contact with it, 
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