22 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
such centers existed in the Scyphomeduse. 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 Scyphomedusz 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 ight 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 
