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ME. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAE. 
§ 5. Bate of Transmission of Stimuli in Aurelia aurita. (A) Contractile Waves . — 
(a) The rate at which contractile waves traverse spiral strips of Aurelia is variable. 
It is largely determined by the length and width of the strip, so that the best form of 
strip to use for the purpose of ascertaining the maximum rate is one which I shall call 
the circular strip. A circular strip is obtained by first cutting out the central bodies, 
i. e. polypite and ovaries, and then, with a single radial cut, converting the animal from 
the form of an open ring to that of a continuous band. I distinguish this by the name 
“ circular ” band or strip, because the two ends tend to preserve their original relative 
positions, so giving the strip more or less of a circular form. Such a strip has the 
advantage of presenting all the contractile tissue of the swimming-bell in one conti- 
nuous band of the greatest possible width, and is therefore the form of strip that 
yields the maximum rate at which contractile waves are able to pass. The reason why 
the maximum rate should be the one sought for is because this is the rate which must 
most nearly approximate the natural rate of contractile waves in the unmutilated 
animal. This rate, at the temperature of the sea and with vigorous specimens, I find 
to be 18 inches per second. 
( b ) In a circular strip the rate of the waves is uniform over the whole extent of the 
strip ; so that the time of their transit from one point to another varies directly as the 
length of the strip. But on now narrowing such a strip, although the rate is thus 
slowed, the relation between the narrowing and the slowing is not nearly so precise as 
to admit of our saying that the rate varies inversely as the width. The following figure 
will serve to show the proportional extent to which the passage of contractile waves is 
retarded by narrowing the area through which they pass: — 
Time from end to end of a circular strip 
Time after width has been reduced to one half . . . 
Time after width has been reduced to one quarter . 
Time after width has been reduced to one eighth . . 
Fig. 10. 
regarding them as muscle-waves, notwithstanding the difficulties connected with their sudden blocking in spiral 
strips &c., or regarding their passage as due to nervous elements, notwithstanding the difficulties connected 
with the supposition as to vicarious action which this view necessarily involved. But this year it has been 
shown that these same tissues manifest a function essentially nervous, and that this function is as difficult to 
destroy by section as is that on which the passage of contractile waves depends. And forasmuch as this func- 
tion cannot he regarded as muscular, we are in this case compelled either to adopt the hypothesis as to vicarious 
action of nerve-fibres, or to abandon the whole subject as inexplicable. Thus it is evident that these later 
results affect the previous ones to this extent, that they remove any advantage we should otherwise gain on the 
side of simplicity by regarding the contractile waves as mere muscle- waves ; for, even if we do so regard them, 
we must still face the old difficulty in another form” — KiErNENBERG’s hypothesis as to the possible blending of 
the functions of nerve and muscle in the same tissue-elements having been shown, in a previous part of the 
omitted portion of this paper, to he here untenable. — September 1877.] 
