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 light 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 

 medusae 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.) 



