664 
ME. GL J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAS. 
allowed to remain preserve their irritability longer than the segments from which the 
lithocysts have been removed. The greatest amount of endurance that I have met with 
in these experiments was in the case of an individual cut into eight segments, in such a 
way as to leave one lithocyst in the middle of each arc. Four of the segments were 
then deprived of their lithocysts, and the paralyzed and unparalyzed segments were left 
in the same basin at a temperature of about 45° F. The water was changed once in 
every twenty-four hours, and all the eight segments were perfectly healthy at the end of 
the sixth day. Next night, however, the temperature rose, and in the morning of the 
seventh day all the segments were dead. 
I have dwelt thus at length upon the differences between the results yielded by Dr. 
Eimer’s experiments and those yielded by my own, because, although these differences 
refer to points that were of minor importance at the time when Dr. Eimer published 
his paper — a fact which, doubtless, led this observer, so well skilled in dealing with the 
great and peculiar difficulties that attend such an investigation of these and allied 
organisms, to neglect repeating these subordinate experiments a sufficient number of 
times, — still it will shortly be seen that, at the stage which the inquiry has now 
reached, it is of great importance to be in possession of accurate and precise data with 
regard to the points which we have just been considering*. 
* [I here withdraw from the proof a footnote mentioning the fact that I had obtained histological evidence 
of the presence of nerve-cells and fibres in Aurelia aurita. I withdraw this note because it is now ren- 
dered superfluous by the much more extended and detailed histological researches of my friend Mr. Schafer. 
Perhaps, however, it is desirable to state that my own histological work was merely of a cursory nature, suffi- 
cient only to show that there was here a splendid field for further cultivation. In accordance with my original 
plan, however, I deferred all systematic inquiry concerning the histological part of the subject till the more 
important of the physiological experiments should have been completed — not because I underrated the import- 
ance of a thorough re-investigation of the histology of the Medusae, but, on the contrary, because I deemed such 
a re-investigation to he of so much importance that I hoped best to give it the attention which it deserved by 
postponing this difficult part of the inquiry until I should be able to devote to it my undivided attention. 
But as the physiology of the subject continued to open up more and more, I felt it was undesirable, either, on 
the one hand, to suspend this part of the inquiry, or, on the other hand, any longer to defer a careful develop- 
ment of the histological part. Accordingly I represented the case to Mr. Schafer, who with great kindness 
consented to spend his leisure time in cooperating with me. The highly interesting character of the results 
which he has obtained show how desirable it was to render the histology of the Medusae a subject of elaborate 
scrutiny ; hut as he has communicated these results to the Royal Society, it is unnecessary that I should here 
restate them. I may observe, however, that the elements which he describes were not unfamiliar to me, though 
I hesitated to pronounce with certainty upon their nervous character. But, lest the fibres which Mr. Schafer 
describes as nervous should eventually prove to he the anatomical structures that are concerned in performing 
the physiological functions which I described in my former paper, I adopted in that paper a neutral term whereby 
to designate the nervous tracts whose presence my experiments, and also those of Dr. Eimer, had revealed. 
This neutral term was “ lines of discharge,” a term which is applicable alike to partly or to fully differen- 
tiated nerves. And forasmuch as I still deem it premature to conclude that definite histological elements are 
concerned in the performance of these physiological functions, I think that while treating of the latter it still 
remains desirable to designate their structural correlatives by some such neutral term as “lines of discharge,” 
rather than by any term of a more precise signification. 
I may also take this opportunity of observing that, almost simultaneously with the publication of Mr. 
