E. W. BERGER ON THE CUBOMEDUSA. 15 
amount of labor necessary to force the water out of two openings 
instead of one, namely, past the velarium. Just how much this 
observation bears upon Romanes’ theory of rhythmic contraction, 
that the rhythm is due to an alternate exhaustion and recovery of 
the contractile tissue, as opposed to the ganglionic theory of rhythm 
of physiologists, one does not wish to speculate much. Yet, I feel 
that the observation rather supports this theory. The tissue having 
to do less work, would become less exhausted at each contraction and 
require less time for recovery and hence have a more rapid rhythm. 
I here sum up Romanes’ theory in a few words. The ganglia 
liberate a constant and comparatively weak stimulus, one perhaps 
about minimal. This stimulus sets off the contractile tissue; but as 
the tissue contracts and becomes exhausted the constant stimulus 
becomes, in relation to it, sub-minimal, and it does not contract 
again until it has recovered and the stimulus is again strong enough 
to set it off. The ganglionic theory of rhythmic contraction supposes 
that the gangha liberate stimuli to the contractile tissue at successive 
intervals. Romanes had this theory suggested to him by the rhythmic 
contractions he succeeded in obtaining by subjecting deganglionated 
bells to a continuous but weak faradic stimulus, or by placing them 
into weakly acidulated water, or into 5 per cent. glycerine. Romanes 
claims that his theory better explains muscular tonus and _ the 
contraction of involuntary muscle. He does not, however, hold this 
theory to the exclusion of the ganglionic theory, since’only too often 
does he speak in terms of the latter. He further brings in his 
support the fact that the frog’s tongue, in which no ganglia have 
been demonstrated, can be made to contract rhythmically when 
subjected to a weak and continuous stimulus. He also calls attention 
to the rhythmic contractions seen in the Protozoa, the snail’s heart, 
etc. Finally, physiologists are much inclined to explain the rhythmic 
contraction of the heart and other involuntary muscles, in part, at 
least, as due to a property of the contractile tissue. 
Margin, Radial Ganglia, Nerve—Experiments 18, 21-23, 30.— 
Complete removal of the margin did not stop pulsation; but the 
removal of the radial ganglia stopped it permanently. While this 
experiment seems to have been tried only once, yet, taking into 
consideration the results of other operations, it would seem that the 
principal centers of spontaneity reside in these ganglia. (It should 
