Notes on the Physiology of Chary bdea rastoiiii. S- 



165'^-170\ the main part of the rhopahum turns and hangs down, 

 to the opposite side. That this is due to the presence of the con- 

 cretion is shown by the fact that, after extraction of that body, the 

 longitudinal axis of the rhopalium always remains straight in 

 whatever position the jellyfish may be held. Since the extraction 

 of the concretion does not affect in the slightest degree the swim- 

 ming activity, the concretion seems to serve simply as a weight 

 for keeping the rhopalium properly suspended as was suggested 

 by Berger (/OO p. 8). The rhopalium, as a whole, therefore, can 

 hardly have any value as an organ of equilibrium. 



The taking off" of one, two (opposite or adjacent) or three rho- 

 palia exercises no infl.uence w^hatsoever upon the mode of swimming 

 nor upon the balancing of body. Neither does a momentary 

 paralysis take place after such operations. In this respect C. 

 rastonii differs from C. xaymacana, in which species, while no 

 permanent paralysis takes place after removal of one or two rhopalia, 

 yet it did occur after a third one w^as removed, though this 

 result does not seem to be constant (Berger '00 p. 8). One thing 

 I noticed in C. rastonii deprived of three rhopalia is the fact that 

 it shows a tendency to swim with the side of the remaining 

 rhopalium turned downwards, though this is by no means the rule. 

 The nifluence of the extirpation of the rhopalia upon the number 

 of pulsations I have not as yet satisfactorily worked out, owing to 

 the difficulty of dissociating it from the effect of the shock caused 

 by the operation. 



If a single rhopalium be kept intact, the medusa is of course 

 able to pulsate. As has been shown in other forms, the jellyfish 

 cut into a strip by a spiral incision continues to pulsate, provided 

 a single rhopalium be present. It does not matter whether or no 

 the pedal ganglion remains in the strip. 



