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 
mim.) 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 
