22 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



such centers existed in the Scyphomedusfe. Conant does not state 

 whether the Polyclonia margin in question was kept in fresh sea- 

 . water or whether the water was not changed during the seven days. 

 If the latter is the case, then some poisonous compounds may have 

 been formed that acted as a stimulus much as weakly acidulated 

 water served Romanes in producing rhythmic contractions in 

 deganglionated bells. 



Again, while it is true that no ganglia are known to exist in the 

 margins of the Scyphomedusae outside of the ganglia in the marginal 

 bodies, yet, ganglion cells and nerve fibers are found in the sub- 

 umbral part of the margin as well as in the rest of the umbrella. 

 And as I know no reason why scattered ganglion cells may not 

 function as ganglia, it is possible that the contractions in question 

 were spontaneous. 



Finally, is it possible that the remaining ganglion originated 

 the contractions in different parts of the margin, thus acting 

 at a distance from the points at which contractions originated? 

 Romanes gives an instance in which he believed to have evidence 

 that this was the case. Upon a final consideration I am inclined 

 to this latter explanation. 



SUMMARY. 



Summing up for Charybdea, we have seen that it is very sensitive to 

 light, strong light as also darkness inhibiting pulsations, while 

 moderate light stimulates it to activity. Also, a sudden change from 

 weaker to stronger light, or vice versa, may inhibit or stimulate to 

 activity respectively. This behavior of Charybdea seems to be 

 correlated with its habit of life on the bottom. We have no 

 reason to doubt but that the eyes of the sensory clubs are the seat 

 of light sensation. 



The experiments on equilibration are negative, giving us no 

 certain light on the function of the concretions, though it appears 

 that they may serve, in part at least, for keeping the sensory clubs 

 properly suspended. Their function in giving the animal sensations 

 of space relations is not, however, excluded. 



Excision of the sensory clubs demonstrates that they are the seat 

 of important ganglionic centers, the removal of which results in 

 temporary paralysis and weakness. That they also are the seat of 

 organs (eyes, network-cells, concretions) that are of importance in 



