MR. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSJ2. 
711 
To settle this point I tried gently pinching the margin with a fine pair of forceps : in 
answer to every nip I obtained a general spasm. I then tried nipping the general con- 
tractile tissue a millimetre or less from its line of junction with the marginal tissue: I 
obtained a general spasm. I next applied similar irritation two millimetres from the 
margin, and obtained no contraction of any kind on the part of the bell as a whole ; but 
in the immediate neighbourhood of the irritation (i. e. about a quarter of an inch on 
either side of it) I obtained a local spasm. On now similarly irritating another point 
of the general contractile tissue, about another millimetre inwards from the margin, a 
still slighter local spasm was the result ; and on repeating the experiment another mil- 
limetre or two from the margin no response of any kind was given. The same experi- 
ments were then conducted on one of the radial tubes, and they yielded the same results, 
with the exception that a general spasm was not of so certain occurrence in answer to 
nipping such a tube as it Avas in ansAver to nipping the margin. From these experiments, 
then, we see that there is no sharp line of demarcation between the tracts of tissue that 
are able to originate a spasm and those that are not. Nevertheless, I think the proba- 
bility is that in these experiments the general and local spasms Avhich resulted on irri- 
tating a point of the contractile tissue very near to one of these tracts, were really due 
to a slight sympathetic action on the part of the marginal or radial tube tissues Avliieh 
were so near to the actual point of irritation ; for it must be remembered that such a 
local spasm could not have been obtained by irritating any other part of the general 
muscle-sheet of Staurophora laciniata. 
( d ) The next question I undertook to answer Avas the amount of section which the 
excitable tissues of Staurophora laciniata would endure without losing their poAver 
of conducting the spasmodic contraction from one of their parts to another. This was 
a very interesting question to settle, because, it may be remembered, Staurophora 
laciniata , like all the other species of discophorous naked-eyed Medusae, differs from 
Aurelia See. in that the ordinary contractile waves are very easily blocked by section*. 
It therefore became very interesting to ascertain Avhether or not the spasmodic Avave 
admitted of being blocked as easily. First, then, as regards the margin. In my former 
paper I stated that if this be all cut off in a continuous strip with the exception of one 
end left attached in situ, irritation of any part of the almost severed strip will cause a 
responsive spasm of the bell, so soon as the wave of stimulation has time to reach the 
latter. This year, therefore, I continued this form of section into the contractile tissues 
themselves, carrying the incision round and round the bell in the form of a spiral, as 
* As stated in the Postscript of my former paper, “ there appear to be important differences between the 
discophorous naked-eyed Medusae and the true Discojohora in this respect ; for in all the species of the former 
which I have as yet observed, the area of paralysis in the nectocalyx corresponds much more precisely with 
the line of ganglionic tissue which has been removed from its margin, than it does in the case .of the true 
Discophora.” I may here explain that this is not, of course, intended to mean that in no case is the spread of 
a contractile wave observable in the tissues of such naked-eyed Medusae; but merely that such spread is 
usually far less extensive than it is in the case of the covered-eyed Medusae. 
