694 MB. G. J. EOMANES ON THE LOCOMOTOE SYSTEM OE MEDUSAS. 
we have in this a very conclusive proof of the truly reflex character of the action we 
are considering ; for after the removal of the marginal ganglia, the mutilated nectocalyx, 
although it remains most keenly sensitive to the gentlest stimulation applied to its 
own irritable tissues, will allow itself to be dragged through the water as rapidly as 
possible by means of the polypite without giving a single contraction. But, in this 
experiment, if the smallest atom of marginal tissue be left in situ , the ganglion cell or 
cells contained in that atom will suffice to preserve the reflex action. In this case, 
however, the responses are neither so ready nor so sure as they are when a larger amount 
of ganglionic matter is concerned in the process. 
(B) Nervous connexions between the Tentacles of Sarsia. — When one of the four ten- 
tacles of Sarsia is very gently irritated, it alone contracts. If the irritation be slightly 
stronger, all the four tentacles, and likewise the polypite, contract. If one of the four 
tentacles be irritated still more strongly, the bell responds with one or more locomotor 
contractions. If in the latter case the stimulus be not too strong, or, better still, if the 
specimen operated on be in a non-vigorous or in a partly ansesthesiated state, it may be 
observed that a short interval elapses between the response of the tentacles and that of 
the bell. Lastly, the polypite is much more sensitive to a stimulus applied to a tentacle, 
or to one of the marginal bodies, than it is to a stimulus applied at any other part of 
the nectocalyx* *. 
These facts clearly point to the inference that nervous connexions unite the tentacles 
with one another and also with the polypite — or, perhaps more precisely, that each 
marginal body acts as a coordinating centre between nerves proceeding from it in four 
directions, viz. to the attached tentacle, to the margin on either side, and to the poly- 
pite. This, it will be observed, is the distribution Avhich Haeckel describes as occurring 
in Geryonia , and Schultz as occurring in Sarsiaf. It is further the distribution to 
which my explorations by stimulus of last year would certainly point. But, in order to 
test the matter still more thoroughly, I tried the effects of section in destroying the 
direction, which is to he immediately considered in the text (B). And as it seems prohahle that in such a simple 
case as this the same nerves would serve to convey impressions in both directions, perhaps the most judicious 
view to take of the difference between the degree of sensitiveness displayed by the polypite when a tentacle is 
injured, and that displayed by the tentacles when the polypite is injured, is to suppose that in the former case a 
feeble ganglionic discharge is added to the stimulus, which discharge would of course he absent in the latter case. 
* These facts were partly ascertained by the method of experimentation described in the last footnote. It 
must here he added that in conducting such experiments the greatest care must he taken not to agitate the 
drops of water in which the animal is contained. The disturbance caused by capillarity on introducing the 
needle-point into these few drops of water is sufficient to cause the tentacles and polypite to contract, even 
though they be a long way off. I therefore used two object-glasses separated by a small interval, so as to break 
the continuity of the water between the point of irritation and that of the tissue whose physiological connexions 
with such point I wished to ascertain. 
f 1 Ueber den Bau von Syncoryne Sarsia und der zugehorigen Medusa Sarsia tubulosa ,’ by Dr. E. E. Schultz 
(Leipzig, 1873). My attention has been directed by my friend Professor Lankester to this admirable little 
monograph on Sarsia. The histological elements to which the author ascribes a nervous function are quite 
familiar to me, and I think that at any rate some of his views with regard to them are probably correct. 
