702 
MR, Gr. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAE. 
(B) Nervous connexions between the JSfectoccdyx and Polypite of Tiaropsis indicans. — 
(«) In the last subsection we have virtually seen that if we have regard to function alone 
the localizing action of the polypite of Tiaropsis indicans may properly be termed a 
reflex action, but that if we have regard to the structure or mechanism by which this 
action is performed we cannot properly so term it. We have virtually seen this, 
because Ave haA^e seen that at least one element essential to the mechanism whereby 
reflex action is effected — the element, namely, of a definite localized ganglion — is here 
absent. The next question, therefore, Avhich arises is, as to whether the other elements 
Avhich are usually considered essential to the performance of reflex action are likeAvise 
absent — the elements, namely, of afferent and efferent nerves. Now I felt so persuaded 
of the difficulty of answering this question by means of histological research, that 
hitherto I have postponed the latter, and, giving priority to the method of section, 
I obtained the most definite results with regard to function which it is possible for this 
or for any other method to yield. 
(Jj) Bearing in mind that in an unmutilated Tiaropsis indicans the polypite invariably 
localizes Avith the utmost precision any minute point of irritation situated in the bell, 
the significance of the folloAving fact is unmistakable, viz. that Avhen a cut is intro- 
duced between the base of the polypite and the point of irritation in the bell, the 
localizing power of the former as regards that point in the latter is wholly destroyed. 
For instance, if such a cut as that represented at a (see Plate 30. fig. 1) be made in 
the nectocalyx of this Medusa, the polypite Avill no longer be able to localize the seat of a 
stimulus applied below that cut, as, for instance, at b. Noav, having tried this experi- 
ment a number of times and having always obtained the same result, I conclude that 
the nervous connexions betAveen the bell and the polypite which render possible the 
localizing action of the latter, are connexions the functions of Avhich are intensely 
specialized, and the distribution of Avhich is radial. 
(<?) So far, then, we have highly satisfactory evidence of tissue tracts performing the 
function of afferent nerves. But another point of great interest arises. Although in 
the experiment just described the polypite is no longer able to localize the seat of 
stimulation in the bell, it nevertheless continues able to perceive, so to speak, that 
also found that such a “headless tentacle” continued to he influenced by stimuli applied to the glands of 
neighbouring tentacles — the headless one in that case bending oyer in whatever direction it was needful for if 
to bend in order to approach the seat of stimulation. This shows that the analogue of ganglionic function 
must here be situated in at least more than one part of a tentacle ; and I think it is not improbable that, if 
trials were expressly made, this function would be found to be diffused throughout the whole tentacle. 
Of course in here using the term “ analogue of ganglionic function,” I do not commit myself to supposing 
that any thing resembling ganglionic structure occurs in any part of Drosera. On the contrary, I have here 
alluded to the case of Drosera just because it is a case in which we cannot expect to meet with any such 
structure, and therefore a case confirmatory of the views to which, I think, my own investigations point — viz. 
that before the functions of ganglion are localized in any characteristic histological structure, they occur in a 
more or less diffused manner in primitive contractile tissues. But as yet I have not had time to give the his- 
tology of Tiaropsis inclicans the attention which it deserves. 
