202 MR. G. J. ROMANES ON THE LOCOMOTOR SYSTEM OF MEDUSAE. 
being demonstrated, and in this connexion they cite the observations of Claus, who 
describes numerous ganglion-cells as occurring in the subumbrella of Chrysaora. It 
is needless to remark how fully the anticipations of these authors have in this respect 
been realised by the researches of Mr. Schafer. 
Lastly, these authors compare the nervous system of the naked-eyed with that of 
the covered-eyed Medusae, with the view of indicating the points which show the 
latter to be much less completely developed than the former. These points are, that 
in the nerve-centres of the covered-eyed Medusae there are no true ganglion-cells, or 
only very few; that the mass of the central nervous system is very small, so that all 
the nerve-centres taken together contain far fewer nerve-fibres than do the nerve-rings 
of the naked-eyed Medusae; and that the centralization of the nervous system is less 
complete in the covered-eyed than it is in the naked-eyed Medusae, as shown by the 
multiplication of similarly formed nerve-centres which occurs in the latter group. 
In this memoir the authors also supply an interesting description of the structure 
of the sense organs in various species of Medusae ; but it seems scarcely necessary to 
extend the present resume of their work by entering into this division of their subject. 
Within the last few weeks Drs. Hertwig have supplemented the work which I 
have thus briefly epitomised with another valuable contribution to the morphology 
of the Medusae. This is entitled ‘ Der Organismus cler Medusen und seine Stellung 
zur Keimblattertheorie.’ As, however, this memoir has no special relation to the 
locomotor system of the Medusae, it does not appear to require in this paper any 
special consideration. 
