E. W. BERGER ON THE CUBOMEDUSA. 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 toa 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 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, ikewise 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’ conclusion, that no 
