Regeneration in Rhizostoma Pulmo. 79 



sensory bodies, and several of the oral arms were excised. In 

 other specimens a varying number of the rhopalia were excised, 

 and in one case all the oral arms were cut off close to the gastric 

 enlargement and on one side including a portion of this organ 

 itself. 



I shall not undertake to transcribe in detail the records of each 

 day, but give rather summaries of results as briefly as is com- 

 patible with clearness, trusting that nothing of importance may 

 be sacrificed in the attempt to bring the records within as brief 

 compass as possible. 



One of the first effects distinguishable in these and following 

 experiments was the evident quickening of the pulsations of the 

 medusae by the process of excision of the organs, or similar op- 

 eration. Not only was the rate of the rhythm greatly increased, 

 passing from about seventy pulsations per minute as an average 

 for medusae of this size, to ninety, or even one hundred per 

 minute. And this rate continued during the entire day, or at 

 every observation, which was quite frequent, and well on into 

 the second day, when the rate fell to ninety and later to eighty; 

 but it was not till the third day that the rate had fallen to the 

 normal of seventy per minute. An examination at this time 

 showed an evident healing of the wounds and some signs of re- 

 generation. Had this been restricted to the sensory bodies it 

 might have been interpreted as signifying some important rela- 

 tion of these organs to rhythmic activity, but the fact that similar 

 effects were produced upon specimens which had not been de- 

 prived of their rhopalia would sufficiently negative such an in- 

 ference. 



Eimer, '74, had noted such an effect following a division of 

 medusae, particularly those which had been divided into halves 

 or fourths, and had undertaken to show that it was chiefly an 

 expression of the reduced size of the organism due to its division, 

 citing the normal rhythm of specimens of varying size as strongly 

 suggesting such an inference. 



Romanes, '85, however, was not able to confirm Eimer's con- 

 tention either in reference to matter of fact or the cause assigned. 

 Romanes, while citing the variation as to the rate of rhythm in 



