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JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
[In other experiments Conant shows that it is not the stimulus 
of walking that causes them to swim when carried into the room, 
for they would not swim when he walked with them on the porch. 
Also, he shows how they may change, some swimming, others not, 
when left for some time in any one place.] 
7. In a tumbler were two pulsating very vigorously. Placed in 
the bright sunlight, very little breeze now and then, they showed no 
change whatever. 
8. Some in a jar were covered with a black coat. The coat was 
taken off, and almost immediately they stopped pulsating, or pulsated 
but feebly, and sank to the bottom. The coat was put on again with 
one part near the bottom of the jar exposed. Almost at once, the 
animals, which were quite motionless, pulsating but little, resumed 
pulsation, which became more and more vigorous, and quickly swam 
to the top again. It seems plainly to be a reaction to light. [Such 
experiments as this were repeated at different times with very like 
results. ] 
9. A bucket with several bobbing actively on the surface was set 
out in a smart shower, and the animals continued bobbing on the 
surface as before. I could not see that they made the slightest 
attempt to go below. 
There can be no doubt but that there is an individual difference 
in sensitiveness to the reaction of light after darkness. E. g., I just 
removed the coat from a dish with four in it; one went to the bottom 
at once, another presently, a third remained active at the surface, 
the fourth when noticed was on the bottom. 
There is also a difference in the length of time they stay on the 
bottom as well as in the quickness in the response to hght. Some 
recover very quickly, should say in less than a minute, and at once 
become very active. Some stay for a long time and only resume 
activity upon the coat being placed over them. Perhaps this explains 
some of the observations in Experiment 1. 
Sensory Clubs.—10. All four concretions were removed and the 
animal stood the operation well. It swam more restlessly, however, 
than others did in the same surroundings. It seemed at first to show 
a trace of loss of sense-perception. It swam up, and down again, 
more changeable than those intact, which stay rather more constantly 
either on the bottom or at the surface. This may, however, have been 
