NERVOUS SYSTEM OF AURELIA AURITA. 
571 
whole, the cells of the basal portion. But in those which are pigmented, and which 
we may suppose to be concerned with visual perception, we meet with some modifi- 
cations (fig. 10, C D). The outer extremity of the cell is much enlarged, and contains 
the whole of the pigment, and from the middle of this wide and generally convex 
free end there extends a very long filament of exquisite fineness. The fixed end of 
the cell is prolonged from the nuclear dilatation as a straight, very delicate thread, 
which usually shows one or more minute varicosities. Its branches become lost in 
the network of cell processes which forms the subjacent fibrous stratum.* 
October, 1877. 
Description oe the Figures. 
Fig. 1. Part of the plexus of nerves covering the muscular sheet, taken about midway 
between the margin and the polypite. Fusiform bipolar nerve-cells are 
seen on some of the fibres. The direction of the muscular fibres is indi- 
cated by the slightly curved lines. Drawn under a magnifying power of 
about 140 diameters, but not to scale. 
Fig. 2. Part of the same plexus, from over a nutrient tube. The vertical striation is 
intended for shading only ; not, like the transverse lines, to indicate the 
direction of the muscular fibres. 
Fig. 3. Part of the same plexus, from near the margin of one of the genital sacs. 
Three cells are observed amongst the nerve-fibres which somewhat 
resemble the nerve-cells, but are of irregular shape, and possess no nerve- 
fibre processes. 
Fig. 4. Margin of an Aurelia near a lithocyst, showing the manner in which the 
nerve-fibres of the subumbrellar plexus converge towards the attachment 
of the lithocyst. The lithocyst has been removed from the place marked l 
in the figure. Less magnified than the three preceding figures. 
Fig. 5. Part of the sub muscular plexus of Aurelia, more highly magnified. 
c. A tripolar nerve-cell. These occur but rarely, 
c, c. Bipolar nerve-cells. 
Drawn under a power of about 300 diameters. 
* Since tbis article was written, a paper (‘ Ueber das Nervensystem und die Sinnesorgane der Medusen,’ 
Jena. Zeitscbr., 1877), by O. and R. Hertwig, lias come to band, wbicb contains a preliminary notice of 
microscopical observations upon tbe nervous system and sense-organs of the Medusae. The authors appear 
to have chiefly studied these structures in the craspedote forms, but they also record observations upon 
two or three genera of the acraspedote Medusae. The extensively distributed nerve-fibres and bipolar cells 
here described as covering the muscular sheet in the latter seem to have escaped their observation, but 
their account of the structure of the lithocysts and the modified epithelium in their neighbourhood in 
other species of Medusas, so far as can be made out from the brief preliminary statement, corresponds in 
the main with the observations here recorded upon the similar structures in Aurelia. 
