8o Charles IF. Hargitt. 



specimens of similar size, is inclined to emphasize what he terms 

 the prepotent influence of certain of the lithocysts (rhopalia) in 

 coordinating the rate of movement, and the presence or absence of 

 such prepotent organs in the portions of medusae under exam- 

 ination. 



Forbes, '48, had long previous called attention to the fact of 

 these quickened movements under the influence of various stimuli, 

 citing particularly a result of an experiment which he had made 

 of a similar character to those which I have cited above. In an 

 experiment in which he had, as he expresses it, "paralyzed one 

 half of the animal" by cutting out the rhopalia from one side, he 

 finds "that the other half contracted as usual, though with more 

 rapidity, as if the animal were alarmed or suffering." He remarks 

 farther that "all medusae when irritated become much more rapid 

 in their movements and contract or expand their disks or bodies In 

 a hurried and irregular manner, as if endeavoring to escape from 

 their persecutors." (Naked Eyed Medusae, p. 3.) 



While in certain details the conclusions of Forbes may be ques- 

 tioned, of his general observations as to matters of fact there 

 can hardly be doubt. Furthermore, whether the suggestions of 

 either Eimer or Romanes are more than approximate guesses, 

 the later observations of Uexkiill have rendered doubtful. So far 

 as my own experiments have gone they hardly touch the problem 

 of the cause of such reactions. We may safely conclude that, in 

 any case, they are of the nature of responses to any continued 

 physical stimulus, such as the experiments under consideration cer- 

 tainly were. With the healing of the wounds there would of 

 course ensue a decline of the irritation, which in turn would be 

 followed by a return to the normal rate of rhythm. 



On May 26th, or two weeks following the operation, the me- 

 dusae had measurably regenerated all the excised organs. The 

 notches cut In the umbrella margins had grown out to complete 

 the normal symmetry and there had been developed in the areas 

 the characteristic purple pigment, differing from the color of the 

 uninjured portions only in its Intensity. The new rhopalia were 

 apparently normal in everything save size and pigmentation. 



It is rather noteworthy that in these experiments certain of the 



