ME. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDUSAE. 
661 
the immediately surrounding tissues. At any rate, so long as this possible explanation 
has not been thoroughly excluded by experiments conducted on the converse method of 
removing the lithocysts from between the arms of the contractile zone, so long, it seems 
to me, must the method we are considering be valueless. The question, then, must be 
decided by the converse method just alluded to, and by it alone. Now I have made 
experiments according to this method, and, so far as I remember, in every case, when 
sufficient care was taken to remove all the lithocysts, the contractile zone entirely ceased 
its contractions. And not only so, but by removing, with the aid of a well-pointed 
scissors, the little sac of crystals composing the central part of the lithocyst, without 
injuring the curious wing-like appendages by which this sac is partly surrounded*, and, 
conversely, by removing in other specimens these wing-like appendages alone, without 
injuring the little sac of crystals — by these experiments I was able to satisfy myself that 
the whole spontaneity of the lithocyst appeared to be exclusively lodged in (or about) 
the minute sac of crystals referred to.” 
To these statements I have only to add that scores of experiments on Aurelia aurita 
have this year invariably confirmed those of last year. In no one instance have I been 
able to detect any physiological evidence of the presence of ganglionic matter in the 
w contractile zones.” In most instances, of course, occasional contractions were given 
after removal of the lithocysts alone ; but I was never able to observe that the sponta- 
neity in these instances proceeded more exclusively, or more frequently, from the 
contractile zones than from any other part of the general contractile tissue. For after 
allowing the animal to recover from the shock consequent upon removal of its lithocysts 
alone, and then observing the degree of spontaneity it manifested, I was in no case able 
to perceive that by now removing all the contractile zones, this degree of spontaneity 
was in the smallest degree diminished'!'. 
This allusion to the spontaneity manifested by Aurelia aurita after its lithocysts have 
been removed, leads to the next point of difference between Dr. Eimer and myself. 
For the sake of conciseness, I shall again quote from my Postscript : — “ I cannot quite 
assent to the description which Dr. Eimer gives of the contractions which sometimes 
supervene in the umbrella of Aurelia aurita when all the lithocysts have been removed. 
He describes them as £ several irregular , inefficient , and feeble contractions of a local 
nature which rarely last any considerable time.’ This is no doubt partly true of some 
cases, but it is not true of all. I have frequently seen these after-contractions as rhythmical 
(though this is rare), as effectual, and as powerful as those which had been previously 
supplied by the single remaining lithocyst. Moreover, these contractions may usually 
be seen to emanate from some very localized portion of tissue, and from thence to 
radiate over the whole substance of the umbrella, just as the contractile waves which 
* The “wing-like appendages” here referred to are shown by injection to he minute diverticula of the 
nutritive-tube system. 
t [In this connexion I may observe that Mr. Schafer has shown the “ nerve-epithelium ” to be exclusively 
confined to the region of the lithocysts. — 1878.] 
5 A 2 
