14© THE POPULAR SCIENCE MONTHLY 



trials it will regularly swallow the meat but usually discard the filter- 

 paper. Thus it would appear that the sea-anemone had detected the 

 deception practised on it in the beginning and had learned to circum- 

 vent the experimenter. But further observations show how erroneous 

 this interpretation is. If the experiment just described is performed 

 on a limited group of tentacles on one side of the oral disk and, after 

 the animal has arrived at the stage of discriminating between meat and 

 paper, the experiment is repeated on another and distant group of ten- 

 tacles, it is found that these tentacles and the part of the mouth next 

 them will accept both meat and paper as the first group did and the 

 same process as was used on this group must be repeated on the second 

 group in order to bring it to the stage of discrimination. Thus it is 

 clear that, however we may regard these acts, Metridium shows no 

 marked power of making the experience of one part of its body serve 

 another; in other words, it shows no decided evidence of a central 

 nervous organ. 



This conclusion is in substantial accord with the recent results 

 obtained by Fleure and Walton (1907) from experiments on Actinia 

 except that they believe that the repeated trials on the tentacles of one 

 side of the circle had in this form a slight influence on those of the 

 other. This influence, however, was so slight that they declared that 

 experience of this kind certainly did not become the possession of the 

 animal as a whole. 



Not only is there in these reactions absence of any strong evidence 

 in favor of well-marked central nervous functions in anemones, but it 

 is very doubtful if we are justified in regarding the local reaction just 

 described as a true discrimination. Jennings (1905) has suggested 

 that sea-anemones possess sensations of hunger and that as the experi- 

 ment proceeds the animal's hunger diminishes and it finally discards 

 when less hungry what it at first accepted. But Allabach (1905) has 

 shown that the same so-called discrimination is arrived at if the sea- 

 anemone is not allowed to swallow anything, but is robbed of meat and 

 paper alike by having these materials picked out of its gullet just as 

 they are about to be swallowed. In fact it seems quite clear that this 

 process of apparent discrimination is in no sense due to centralized 

 nervous functions, but is merely the result of exhaustion. At the 

 beginning of each experiment the receptors are stimulated by the strong 

 juices of the meat and the weaker juice of the paper. As they run 

 down in efficiency, they come to a stage where they no longer react to 

 the weaker stimulus of the paper and respond only to the meat. At 

 this stage apparent discrimination takes place. 



ISTot only do these experiments show no evidence of central nervous 

 functions, but they indicate a decided looseness of nervous articulation. 

 The activity of one side of the body of the sea-anemone has very little, 



