8 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
Concretions—Experiments 10, 11—The four concretions were 
removed from each of four animals. Two of these (Experiments 10, 
and another (X), not appended, to save space) seemed to be little if 
at all affected by the operation. One of the two (10) swam actively, 
at first up and down more changeably than those intact, but later 
mostly near the surface. The other one also swam actively and 
showed nothing to indicate weakened sense-perception. The other 
two (11) did not stand the operation well, as Conant remarks, and 
immediately went to the bottom, where they remained, one swimming, 
while eight hours later one was still in good condition. 
Several attempts with stronger light by removing the coat from 
the jar made no difference in the behavior of 10; it continued to 
swim as heretofore. Upon a final trial, however, with removing the 
coat, it went to the bottom, thus showing a possible reaction to light; 
but when next seen it was keeping to the bottom. 
That the concretions should function as organs of ight sensation, 
as the first of the above animals might seem to indicate, I believe is 
out of the question.* The fact, too, that this same animal (10), together 
with another (X), swam actively, immediately changing their course 
upon coming to the surface, in reality behaving quite as normal 
animals, hardly permits us to conclude from the behavior of the 
other two (11) that the concretions function directly as organs of 
equilibrium or space relations. May these concretions not function 
simply as weights for keeping the sensory clubs with their eyes 
properly suspended? Since these concretions lie at the lowermost part 
of the clubs and in closed sacs and unsupported by cilia, it would 
seem that the above suggestion as to their being weights is not 
improbable. Direct observation (Experiment 20) by Conant shows, 
furthermore, that the clubs always hang with a tendency for the 
concretions to be lowermost, regardless of the position of the animal. 
Again, while they may function as weights, as just explained, 
the fact that the epithelium of the clubs is flagellated (a flagellum, 
continued as a nerve fiber, to each cell—see Histology), the supposition 
lies near that these flagella are the ones influenced by the concretions 
as the clubs bear against one side of the sensory niche or the other. 
*It was at one time supposed that the concretions in the marginal bodies of 
medusze represented lenses and the surrounding nerve tissue the optic nerve, a 
supposition so highly improbable that it never gained any acceptance. (Ib., p. 
41, note.) 
