ME. Gr. J. EOMANES ON THE LOCOMOTOE SYSTEM OF MEDTJSiEi 
709 
On the whole, then, with regard to Tiaropsis indicans, I conclude in favour of some- 
thing resembling a plexus of functionally-differentiated tissue-lines pervading the whole 
inner surface of the nectocalyx. A number of these tissue-lines I conceive to pursue, 
in a functional sense, a radial course ; and, therefore, when intact, to enable the.polypite 
correctly to localize a seat of irritation. Others of these lines I conceive to pursue 
various courses, and in so doing to connect the radial lines with one another. All the 
lines of such a plexus I conceive to be capable, in a high degree, of vicarious action ; 
and I am inclined to suppose that a large proportional number of such lines are aggre- 
gated in the courses of the four radial tubes. But in now taking leave of the interesting 
series of facts which have led to these inferences, I should like to observe that, while I 
know the former cannot be modified by future investigation, I feel the latter may thus 
be shown imperfect or untrue. It has not seemed to me, however, that this is a suffi- 
cient reason to avoid speculation at the stage which my inquiries have now reached. 
There can be no doubt that the facts concerning Tiaropsis indicans are of a highly sug- 
gestive character ; and I think it will shortly be found desirable thus to have paved the 
way towards arriving at some sort of conception with regard to analogous, though far 
more astonishing, facts which are presently to be adduced concerning Aurelia aurita. 
§ 3. Character of the Nervo-muscular Tissue of Staurophora laciniata. — ( a ) The few 
individuals of this species which I was this year able to procure I utilized in the study 
of those peculiar spasmodic movements to which allusion was made in my former paper. 
These movements, it will be remembered, never occur spontaneously, but only in response 
to stimulation of certain parts of the organism, under which condition they never fail to 
occur. It will further be remembered that these spasmodic movements consist of a 
sudden and most violent contraction of the entire muscle-sheet, the effect of which is to 
draw together all the gelatinous walls of the nectocalyx in a far more powerful manner 
than occurs during ordinary swimming. In consequence of this spasmodic action being 
so strong, the nectocalyx undergoes a change in form of a. very marked and distinctive 
character. The corners of the four radial tubes, being occupied by comparatively resist- 
ing tissue, are not so much affected by the spasm as are other parts of the bell ; and 
they therefore constitute a sort of framework upon which the rest of the bell contracts — 
the whole bell thus assuming- the form of an almost perfect square, with each side pre- 
senting a slight concavity inwards. These spasmodic movements, however, are quite 
unmistakable, even when they occur in a very minute portion of detached tissue ; for 
however large or small the portion may be, when in a spasm it folds upon itself with the 
characteristically strong and persistent contraction. I say “ persistent contraction” because 
it will be remembered that a spasmodic contraction, “besides being of unusual strength, is 
also of unusual duration.” That is to say, while an ordinary systolic movement only lasts 
a short time, a spasm lasts from six to ten seconds or more, and this whether it occurs in a 
large or in a small piece of tissue. Again, it will also be remembered that the diastolic 
movements differ very much in the case of an ordinary locomotor contraction and in that of 
a spasm ; for while in the former case the process of relaxation is rapid even to sudden- 
