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XVII. Observations on the Nervous System of Aurelia aurita. 
By Edward Albert Schafer, Assistant Professor of Physiology in University 
College, London. 
Communicated by W. Sharpey, M.D., LL.D., F.Ii.S. 
Received October 31, 1877, — Read January 10, 1878. 
[Plates 50-51.] 
Last August I undertook, at the request of my friend Mr. G. J. IIomanes, an 
investigation with the view of proving the presence or absence of histologically 
differentiated nervous structures in the Medusae. Mr. Romanes’ experiments'* have 
shown the existence of a central nervous apparatus in the marginal bodies of these 
anhnals, and probably also of nervous tracts (lines of discharge) over the lower surface 
of the nectocalyx or umbrella. But up to the present time the anatomical proof of 
the existence of a nervous system in this class has rested chiefly upon the authority 
of Haeckel, who has described! in two genera of the craspedote Medusae a ring of 
nerve-fibres lying on the inner side of the marginal canal, and provided with a 
ganglionic enlargement at the base of each lithocyst. From each of these ganglia four 
nerves are described as passing — one to the polypite, and the others to the adjacent 
tentacles and lithocyst. 
My observations have been chiefly confined to Aurelia aurita, partly because, at the 
time of year chosen, this species furnished the most abundant material, partly on 
account of its having been the subject of the greater number of Mr. Romanes’ 
experiments, and also because the nervous structures can be more readily made out 
in this species than in any other that could be readily got. But preparations of 
a species of Chrysaora make it abundantly evident that ganglion cells somewhat 
similar to those immediately to be described as underlying the muscular sheet in 
Aurelia are found also in this genus, and it is probable that what is true of these two 
genera will apply with but little modification to other genera of acraspedote Medusee. 
Whether a similar distribution of nerves exists also in the Craspedota, is a matter which 
must for the present remain undecided ; my own observations, which were confined to 
species of Thaumantias and Tiaropsis, have so far yielded a negative result. { 
* Phil. Trans., 1876, pp. 269, et seq. ; and Phil. Trans., 1877. 
t Beitriige zur ISTaturgeschiclite der Hydromedusen. 
t See postscript. 
