THE NERVE-NET 123 



accompanied by elongation. It is remarkable how strik- 

 ingly similar to these are the responses of the isolated 

 tentacles to the same juice. To a 1 per cent, solution of 

 quinine hydrochloride in fresh water both classes of ten- 

 tacles respond by quick contractions and often local con- 

 strictions. 



In all the tentacular reactions studied the responses of 

 the isolated tentacles agree most strikingly with those 

 of the normally attached tentacles. Of course, the reac- 

 tions of the isolated tentacles are not exact duplicates 

 of those of the attached ones. They are feebler and less 

 precise, but aside from differences such as these, which 

 are quite clearly of an operative origin, the severed ten- 

 tacle reproduces in a most striking way the responses of 

 the attached tentacle (Parker, 1917 fc). 



The tentacles of Metridium are very small in com- 

 parison with those of Condylactis and in consequence de- 

 tailed tests cannot be carried out on them with the ease 

 and certainty that they can on larger forms. Neverthe- 

 less their general reactions are indicative of great au- 

 tonomy. If the juices from fish flesh and other like food 

 are discharged on the tentacles of an expanded Metrid- 

 ium, these organs will exhibit first a considerable amount 

 of irregular movement and finally point toward the mouth, 

 where in fact under ordinary conditions they would de- 

 liver the food itself. If, now, a tentacle is carefully cut 

 off from Metridium, its original orientation in reference 

 to the animal as a whole being kept in mind, the appli- 

 cation of the stimulating juice will cause it, first, to un- 

 dergo irregular movements and then to point in that di- 

 rection that was originally toward the mouth. It is, 

 therefore, evident that the tentacle of Metridium, like that 

 of Condylactis, has within its own structure the neuro- 



