24 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
changed to bring similar experiments together, while useless and 
often repeated ones have been omitted, and short elliptical sentences 
completed. Where the present writer wished to add any explanation, 
the same has been placed in brackets. 
CHARYBDEA. 
Light and Darkness.—1. Eight meduse, in a deep glass jar and 
covered by a black coat, except one inch around the top, were 
placed in the dark-room. 
a. When light from a lamp was thrown on the surface (one 
inch) layer, the animals were active near the surface; when the 
light was withdrawn, one or two were on the bottom and not moving 
but were probably pulsating. 
b. After four or five minutes in the dark, three or four besides a 
feeble one are on the bottom. It took about two minutes to get them 
all to swim [by the lamp]. Of the three on the bottom, one, at any 
rate, was not pulsating. [Three other attempts like a and b were 
made, with very similar results. ] 
2. Experiment No. 1 was repeated several weeks later. Four in 
a large round glass dish were placed in the dark-room. <A lamp 
being held to the dish all but one were found to be on the bottom. 
That one quickly went to the bottom, while two of those on the 
bottom quickly came to the top. In two or three minutes the one 
that had gone to the bottom began to pulsate and at about the 
same time the other one that had remained on the bottom also 
began to pulsate, while the two that had gone to the top stayed 
there swimming very actively. [Repeated with like results.] 
3. Fresh ones did not show the reaction to light after darkness 
so well as did those in the experiments previously recorded. They 
were experimented with about nine A. M., while usually they were 
tried later in the day. I had rather suspected from previous work 
that they would not react so well when fresh. 
4. a. In walking with the jar (1) of jelly-fish of experiment 1 
from the dark-room to the back porch of the laboratory (fifty steps), 
in the bright sun and a cool breeze, all were found upon entering 
the laboratory door to have settled to the bottom and most of them 
to have ceased active swimming. In five minutes two or three were 
swimming somewhat, and in five minutes more all but one or two 
(eight in all) were swimming. 
