712 ME. Gr. J. EOMANES ON THE LOCOMOTOE SYSTEM OF MEDUSAS; 
represented in the case of Aurelia by Plate 33 of my previous paper. In this way 1 
converted the whole Medusa into a ribbon-shaped piece of tissue'*; and on now stimu- 
lating the marginal tissue at one end of the ribbon, a portion of the latter would go 
into a spasm. The object of this experiment was to ascertain how far into the ribbom 
shaped tissue the spasmodic wave would penetrate. As I had expected, different 
specimens manifested considerable differences in this respect ; but in all cases the degree 
of penetration was astonishingly great. For it was the exception to find cases in which 
the spasmodic wave failed to penetrate from end to end of a spiral strip caused by a 
section that had been carried twice round the nectocalyx; and this is very astonishing 
when we remember that the ordinary contractile waves, whether originated by stimu- 
lation of the contractile tissues, or arising spontaneously from the point of attachment 
of the marginal strip, usually failed to penetrate further than a quarter of the way 
round. But still more astonishing is the fact that these spasmodic waves will continue 
to penetrate such a spiral strip even after the latter has been submitted to a system of 
interdigitating cuts of a very severe description. Here, again, of course, considerable 
individual differences as to tolerance of section occur ; but the drawing in Plate 30 (fig. .3) 
will convey some idea of the surprising amount of tolerance that is sometimes shown. 
This figure explains itself, it having been drawn to measurement from a specimen in which 
the spasmodic waves, started by stimulation of any point in the severed margin a b, 
would penetrate the whole of the strip c d e, wdiile in the same specimen the ordinary 
contractile waves became blocked at d. 
( e ) Now we have here to deal with a class of facts which physiologists will recognize 
as of a perfectly novel character. Why it should be that the very tenuous tracts of tissue 
which I have named should have the property of responding even to a feeble stimulus 
by issuing an impulse of a kind which throws the contractile tissues into a spasm ; 
why it should be that a spasm, when so originated, should manifest a power of pene- 
tration to which the normal contractions of the tissues in which it occurs bear so small 
a proportion ; why it is that the contractile tissues should be so deficient in the power 
of originating a spasm, even in response to the strongest stimulation applied to them- 
selves — these and other questions at once suggest themselves as questions of the highest 
interest : at present, however, I am wdiolly unable to answer them. To assume that 
it is the ganglionic element in the margin, and possibly also in the radial tubes, which 
responds to direct stimulation by discharging a peculiar impulse which has the remark- 
able effect in question — to assume this is not to explain the facts. For the sake of 
rendering the matter quite clear, let us employ a somewhat far-fetched but convenient 
metaphor. We may compare the general contractile tissues of this Medusa to a mass 
of gun-cotton, which responds to ignition (direct stimulation) by burning with a quiet 
* It may be stated that while conducting this mode of section on Stciurophora Icicinicita, the animal responds 
to each cut of the contractile tissues with a locomotor contraction (or it may not respond at all)-; hut every 
time the section crosses one of the radial tubes, the whole bell in front of the section and the whole strip 
behind it immediately go into a spasm. 
