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 is 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, 



