14 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



Pieces of the sides connected only with the stomach and suspen- 

 soria, or with the margin (Experiment 47 (?)) twitched spontaneously, 

 but seldom did so when these were removed. In one instance the 

 whole side was cut out so as to exclude the radial ganglion but still 

 connected with a portion of the suspensoriuni. This pulsated, or 

 contracted, but on being halved transversely, the lower half ceased to 

 contract while the upper half connected with the suspensorium, 

 continued to contract. 



Cutting off the whole stomach end of the animal excited to very 

 rapid pulsations of the remaining part, with the stream of water 

 stronger out the aboral end than past the velarium. 



Conant says, "It seems I get no good evidence of the subumbrella 

 without connection with special nerve centers being able to contract 

 by itself." The piece in which he did get contractions he suspects 

 may have been intimately associated with some part of the frenula 

 or the suspensoria. In Polyclonia no such doubt exists, for small 

 pieces of subumbrella were seen to contract. A small piece of 

 subumbrella of Charybdea with a sensory club attached could contract 

 by itself. 



From the above it would seem that a center capable of inciting 

 to contractions resided in the suspensoria as well as in the sensory 

 clubs, and this may be one of the centers that becomes potent upon 

 the removal of the clubs. This is further supported by Conant's 

 observation (Introduction and "Cubomedusse") that an extra large 

 number of ganglion cells is found under the epithelium of the 

 suspensoria. A somewhat similarly located center of spontaneity 

 described by Romanes for Staurophora laciniata (Hydromedusa) has 

 already been noted. 



As to the rapid pulsations of the bell after cutting out the 

 stomach end, this also is similar to Romanes 1 results on Aurelia and 

 other Scyphomedusse, when he cut off parts of the manubrium or an 

 aboral ring out of the bell. In these instances, however, Romanes 

 soon obtained a slackening of the rhythm following the temporary 

 acceleration. The temporary acceleration he attributes to the stimulus 

 of cutting, and the slackening to a lack of some afferent stimulus 

 from the removed tissue. Conant obtained the same results on 

 Polyclonia by removing the oral arms (see Polyclonia) but says 

 nothing about a slackening of the rhythm in Charybdea. I believe 

 the increased rhythm in Charybdea was in part due to the decreased 



