36 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



A Polyclonia, about four and one-half inches (115 mm.) in diameter, 

 gave twenty-six or twenty-seven regular pulsations to the half- 

 minute. After one otocyst was removed, pulsations continued, but in 

 groups with intervals of pause : e. g., thirteen, pause ; ten, pause ; six. 

 Three minutes after the removal of the lithocyst there were 5, 3, 1, 

 3, 5, or seventeen pulsations to the half-minute. Eleven minutes 

 after the operation there were fifteen to the half-minute. The 

 removed lithocyst and surrounding tissue gave contractions. 



43. May 13th. The Aurelia was in rather poor condition but 

 would pulsate upon being stirred. The other seven lithocysts were 

 removed when only a few contractions originated thereafter. 



The Polyclonia was in good condition, but was pulsating only 

 intermittently when first seen in the morning. When the remaining 

 seven lithocysts were cut out and no more pulsations were observed, 

 the oral arms could still move. 



May 14th. Both were found dead upon returning in the evening. 



44. May 15th. An Aurelia and a Polyclonia were taken in the 

 morning. The Aurelia was two and one-half to three inches (62.5-75 

 mm.) in diameter, with three tufts of phacelli, three oral arms and 

 seven lithocysts. The Polyclonia was normal and seven or eight 

 inches (175-200 mm.) in diameter. 



In the Aurelia all the lithocysts were removed. Spontaneous and 

 coordinated contractions could still occur after time had been allowed 

 for the shock from the operation to pass away. The next day the 

 animal was still alive and pulsating, but ragged, and the next day 

 following was quite dead. 



In the Polyclonia the normal rhythm was fourteen pulsations to 

 the minute. Some pulsations were apparently quicker than others 

 and the intervals were not the same. Thirteen, ten, and twelve 

 pulsations were also counted. After putting the animal into fresh 

 sea-water, it pulsated thirty-three to the minute. Six minutes later it 

 was still pulsating at the same rate, while in four minutes more 

 eleven pulsations, many of which were in groups of two, were noted. 

 In five minutes more it pulsated eleven times to the minute with 

 only one double pulsation. One oral arm was then cut off and the 

 rhythm counted about one minute afterward fourteen pulsations, 

 then a pause of fifteen seconds, then two pulsations, in all sixteen to 

 the minute were counted. About ten minutes later there were eight 

 pulsations, two or three minutes later only three, while in two or three 



