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ME. Gf. J. EO MANES ON THE LOCOMOTOE SYSTEM OE MEDUSAS. 
task of determining the questions before me would prove a comparatively easy one. 
Unfortunately my anticipations were not realized. The conducting-power of the gela- 
tinous tissue (more or less of which is necessarily adherent to the marginal canal), the 
deleterious influence of the air upon the intrapolar portion of tissue which is necessarily 
exposed to it, the voluntary motions of the animal — these, and other elements of 
difficulty which I need not wait to specify, have proved so serious, that, although a 
great deal of labour has been expended upon this part of my subject, I do not yet feel 
myself justified in here giving a definite opinion with regard to it; and I have stated 
the foregoing details chiefly in the hope that the great importance of the inquiry 
may induce some other observer to assist me in conducting it. I may say, however, 
that I have obtained undoubted indications of a state of exalted sensibility in the extra- 
polar regions of the severed strip, although I am unable to say that I have obtained 
any satisfactory indications of a corresponding anelectrotonic state. I am not yet in a 
position to speak confidently with respect to Pflugee’s law*. 
(D) Before leaving the subject of electrical stimulation, there are still a few further 
observations to detail. 
(a) The excitable tissues of Medusae in their behaviour towards electrical stimula- 
tion conform in all respects to the rules which are followed by the excitable tissues of 
other animals. Thus closure of the constant current acts as a much stronger stimulus 
than does opening of the same, while the reverse is true of the induction-shock. 
(|8) As before stated, different species of Medusae manifest different degrees of sensi- 
tiveness to electrical stimulation, though in all cases the degree of sensitiveness is 
wonderfully high. 
(y) When the constant current is passing in a portion of the strip of a severed 
margin, the nectocalyx sometimes manifests uneasy motions during the time the current 
is passing. It is possible, however, that these motions may be merely due to acci- 
dental variations in the intensity of the current. 
(c5) When the intrapolar portion of the severed margin of S. laciniata happens to be 
spontaneously contracting prior to the passage of the constant current, the moment this 
current is thrown in these spontaneous contractions often cease, and are then seldom 
resumed until the current is again broken, when they are almost sure to recommence. 
This effect may be produced a great number of times in succession. 
(a) Exhaustion of the excitable tissue of the nectocalyx may be easily shown by the 
ordinary methods. Exhausted tissue is much less sensitive to stimulation than is fresh 
tissue. Moreover, so far as the eye can judge, the contraction is slower and the period 
of latent stimulation prolonged. 
(£) It is important to observe that the tetanus produced by Faradaic electricity is 
not of the nature of an apparently single prolonged contraction (except, of course, such 
among the naked-eyed Medusse as respond to all kinds of stimuli in this way), but 
* I may here observe that it was in one of my numerous electrical esperiments upon Staurophora laciniata 
that the exception to the fundamental experiment mentioned in Division II. was noticed. 
