806 
MR. a. J. ROMANES ON THE LOCOMOTOR SYSTEM OE MEDITSiE. 
ment*, and added a suggestion that such of the readers of ‘ Nature’ as should have the 
opportunity of repeating this experiment on the other species of Medusae during the 
summer and autumn months of 1875, should do so on as many species as possible. I 
have to regret that no one appears to have acted on this suggestion ; but at the same 
time, I have to express my best thanks to Dr. Lutken for the very valuable reference 
which he has supplied. Dr. Eimer’s paper clearly shows that he made the fundamental 
observation in the case of Aurelia aurita and Cyancea capillata quite independently of 
my suggestion in ‘ Nature; ’ and Dr. Lutken’s reference to this paper has been of special 
value to me from the fact that up to the time when I received it (viz. February 1876) 
no one in England appears to have been aware that Dr. Eimer had done any work in 
connexion with the nervous system of Medusae. This ignorance is to be accounted 
for by the fact that the journal in which Dr. Eimer published his paper has but a very 
limited circulation in this country, while of the paper itself no abstract appears in the 
4 Centralblatt.’ 
The following is a full abstract of the results and opinions set forth by the paper in 
question. 
In Aurelia aurita the author observed that excision of the lithocysts was usually 
followed by complete and permanent paralysis of the swimming-organ, while any tissue 
left adhering to a lithocyst continued rhythmically to contract “ like the excised heart 
of a frog.” He appears, however, to be decidedly of the opinion that the seats of 
spontaneity are not the lithocysts alone, but the entire crescent-shaped interruptions of 
the margin in which the lithocysts are lodged (see Plate 32). He arrives at this conclusion 
because he finds that by progressively lessening the amount of contractile tissue which 
is left adhering to an excised lithocyst, this amount may be reduced to a “ tissue-zone ” 
only a few millims. broad. This crescent-shaped zone, therefore, he always speaks of as 
the “ contractile zone.” Concerning the character of the contractions, Dr. Eimer is of 
the opinion that they are 44 usually involuntary,” but that they are also in a certain degree 
subject to the control of the will. 
The author next proceeds to detail some very interesting observations on the rate of 
the rhythm. He says, what is quite true, that although the pulsations of Aurelia 
are very rhythmical, they are frequently interrupted by pauses of longer or shorter 
duration. Pie says, further, that the duration of pauses bears a direct relation to the 
* In some respects this description was not quite accurate, and for the following reason : — The obser- 
vation was made towards the end of the summer of 1873 on some individuals of the species of Slabberia 
conica. I found that excision of the marginal bodies alone determined complete paralysis of the neeto- 
calyx, and also, apparently, of the polypite. Next year I was unable to pursue the inquiry, but published 
the note in ‘Nature’ above referred to. Last year I continued the research, hut did not happen to fall in 
with any specimens of Slabberia. Erom my observations on the nearly allied form of Sarsia, however, I 
am now inclined to believe that if my specimens of Slabberia two years before had been in a perfectly vigorous 
state, I should have found it necessary, in order to cause complete paralysis of the nectocalyx, to remove 
its entire margin, and not merely the vesicles alone. 
