PHYSIOLOGICAL. 
CHARYBDEA. 
Light and Darkness-—Experiments 1-9, 10, 38, 34.—As already stated 
in the Introduction, a part of Conant’s experiments were performed 
in a photographer’s dark-room, with the animals in a deep glass jar. 
In the dark a fair proportion of the animals became nearly quiescent 
on the bottom, but upon lighting a lamp many started up immediately, 
while others took a longer time to come to the surface and swim. 
These experiments were tried a number of times and on different 
occasions with very similar results. Some medusz, however, tried 
immediately after being brought in, seemed not to react so well upon 
being placed in the dark-room, nor would they become quiescent. 
This, probably, was due to the fact that the animals had not yet 
recovered from the effects of being caught and placed in new 
surroundings. (Experiments 1, 2, 3.) 
Other experiments (4-8, 33, 34) were tried by carrying the jar 
with the animals from the weaker light of a room into the more 
intense light of outdoors or into direct sunlight. The usual result 
was an inhibition of pulsation and a settling to the bottom, while 
the meduse immediately became active again upon returning with 
them to the room. These results were so marked that no doubts can 
be entertained as to their cause, though some exceptions occurred in 
which animals placed in the sun continued to swim on the surface 
or soon recovered pulsation. In some experiments, too, no animals 
responded to the inhibitory stimulus of the brighter light or all very 
soon recovered. (See, however, Temperature.) 
Reducing the light by placing a coat over the jar produced 
the same effect in some experiments (8, 9, 10) as did reducing the 
light in other ways, while removing the coat produced the same 
effect as exposure to brighter light. In these instances it appears 
to be the transition from weaker to stronger light that inhibits 
pulsation, rather than the actual intensity of the light; and vice versa. 
It must be noted, too, that when left for some time in any one place 
