These results on the removal of the lithocysts (and margin in Polyclonia) in Aurelia, Polyclonia and Cassiopœa agree quite with those on Charybdea and, of course, also with Romanes’ and Eimer’s 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 temporary 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’ 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 summation 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.