E. W. BERGER ON THE CUBOMEDUS.E. 21 



results as to paralysis and recovery following the removal of the 

 lithocysts, or margin, in Aurelia, Cyanea, etc. I recall no similar 

 observations, however, on removing a single lithocyst, and the 

 question of an explanation for the slowing of the rhythm thus 

 brought about arises. Romanes gives as an explanation for the 

 slowing of the rhythm (Aurelia, Cyanea, etc.) following the tem- 

 porary acceleration upon removing the manubrium or a portion 

 from the center of the bell, as due to a lack of an afferent stimulating 

 influence upon the ganglia from the excised tissue. May a similar 

 explanation not serve to explain the slowing following the removal 

 of a single lithocyst, above noted? The removed lithocyst could no 

 longer give its efferent stimulus to the remaining ganglia nor to 

 the tissue, so that the former would have a weaker stimulating 

 influence, in consequence of which the latter (the contractile tissue) 

 would be deprived of a part of the original stimulus of the 

 remaining ganglia as also of that of the removed ganglion. The 

 whole would thus result in giving to the contractile tissue a weaker 

 stimulus, which, again, would require longer and greater recovery on 

 the part of the tissue in order to be set off by the stimulus at 

 hand. This explanation is given on the basis of Romanes 1 theory 

 of rhythmic contraction previously explained. 



Of course, it may be suggested that the musculature had lost 

 tonus, due to the lack of influence of the removed ganglion (lithocyst), 

 in consequence of which there was a lowering of irritability on the 

 part of the contractile tissue. This would require a greater sum- 

 mation of stimulating influence (Ganglionic theory of contraction) 

 on the part of the remaining ganglia to set it off. Again, the loss of 

 irritability on the part of the contractile tissue may have been due 

 to a lack of nutritive influence from the removed ganglion. 



Romanes' explanation, that the slowing of the rhythm following 

 the removal of the manubrium and central parts of the bell in 

 Aurelia and Cyanea is due to a lack of an afferent stimulus on the 

 ganglia from the removed tissue, likewise explains the similar results 

 obtained by Conant by removing the oral arms from Polyclonia. 



The fact that a margin of Cassiopoea and also of Polyclonia, 

 connected with but one ganglion, often originated contractions in 

 other parts as well as from the ganglion, seems to show that 

 motor centers resided in the margin outside of the ganglia. This 

 would be somewhat at variance with Romanes 1 conclusion, that no 



