76 Charles W . Hargitt. 



The matter will be referred to in further detail in another con- 

 nection and some reference made as to its probable significance 

 and cause. 



In all cases the primary experiments were made as soon as 

 possible after the medusae were brought into the laboratory. I 

 have said the primary experiments. This refers to the fact al- 

 ready alluded to, that in several cases experiments were variously 

 repeated upon the same specimen. This was in part for the pur- 

 pose of testing the conclusiveness of preceding experiments, and 

 in part owing to the fact that there was an insufficient supply of 

 material to serve the demands of the course of experiments under 

 way. Details as to these aspects will be given in connection with 

 the several experiments described. 



The first experiment was made upon a large specimen, and in 

 order to determine at the outset whether the earlier observations 

 of Romanes and others, that complete removal of the marginal 

 sense organs resulted in complete paralysis of the medusa, these 

 organs were carefully removed by means of triangular incisions 

 as indicated in Figure i, a. The results were substantially con- 

 firmatory of the earlier records, the medusa becoming more or 

 less passive, except for an occasional single contraction at very 

 irregular intervals. This experiment was made on May ii, and 

 the following series of observations will suffice to show the general 

 course of events. It should be added in this connection that along 

 with the excision of the rhopalia several other marginal excisions 

 were made, and that three of the oral arms were cut off close 

 below the region of the gastric enlargement. The aspect of the 

 specimen on the next day was practically the same. While there 

 was an occasional contraction of the bell accompanied by certain 

 'movements of the body, there were no Indications of rhythm. 



May 13th. — The medusa, while apparently in perfect health 

 and vigor of general functions, was still unable to originate any 

 definitely rhythmic movements, though responding to various 

 mechanical stimuli, such as a strong current of water from the 

 tap, or the touch of a glass rod. At various times during the 

 day there was evident a rather marked tendency toward sponta- 

 neous movements, and occasionally something very like a rhythm, 



