REPORT ON THE DEEP-SEA MEDUSAE. 21 



projecting radial-ribs into sixteen deepened radial areae or depressions, which project like 

 lobes on the umbrella margin (PI. VII. fig. 12). Of the sixteen radial ribs ("costse exum- 

 brales "), four perradial and four interradial (in the middle between the former) lie above the 

 mesogonia. These eight principal ribs are distinguished by thin streaks of puqile-red 

 pigment, which pass into eight large red ocellar spots at the umbrella margin, but are 

 wanting in the eight other alternating adradial ribs. All sixteen ribs are tipped with 

 nematocysts, which appear yellowish-white by reflected light and black by transmitted 

 light. These spots of pigment form a broad band in the periphery of the exumbrella 

 above the margin of the umbrella, and are divided from it by a colourless streak. The 

 eight red ocellar egg-shaped spots before mentioned are placed at the distal ends of the 

 eight red pigmented ribs ; they may, perhaps, be considered as true ocelli, though they 

 do not appear to contain a lens (comp. PI. VII. fig. 1). Besides these, there are also 

 sixteen large crescent-shaped golden-yellow spots at the marginal end of the ribs of 

 the exumbrella. The sixteen concave intercostal radial depressions of the exumbrella 

 alternating with these increase in breadth and depth towards the umbrella margin, 

 and are traversed in the middle by a deep-radial furrow (" sulcus exumbrahs "). A 

 pedunculated subradial auditory club lies at the end of these radial depressions (PI. VIII. 

 fig. 8, ok) in the middle of the projecting marginal lobe, and of the bunch of tentacles 

 borne by it. 



The peculiar peripheric umbrella margin (" margo umbralis," PI. VIII. fig. 8) is con- 

 siderably thickened, and armed with a connected urticating ring {tic), consisting of a 

 thick accumulation of thread-cells. The sixteen protuberances or flat lobes are rounded 

 like an arch, and when looked at from above (and also at their subumbral surface) show 

 a cord of cilia pigmented black immediately inside the urticating ring. This ciliated 

 cord is sinous, and forms from eight to ten projecting vessels on each lobe (fig. 8, xp). 

 In the arching inwards of the umbrella margin between each two lobes, at the distal end 

 therefore of each exumbral rib, the black ciliated cord becomes a tongue-shaped pro- 

 jection, showing a funnel-like depression, which may perhaps be an organ of smell 

 (fig. 8, xo). A small free auditory club rises on the outer edge of each of the sixteen 

 marginal lobes enclosing a spheroid or elliptic otolite in the free end (in the last 

 endodermal cell, fig. 8, ok). The auditory club lies nearer the lower margin of the 

 umbrella, inwards from the insertion of the tentacles. More minute investigation was 

 unfortunately impossible. 



The tentacles, which amount to 200 to 260, are divided into sixteen pencil-shaped 

 bunches, each two bunches between each two radial canals. In the transverse section the 

 tentacles are hollow (fig. 4), capable of great extension, movable and contractile, fur- 

 nished with a sucking-disk at the end, and are very similar to the ambulacra! feet of 

 the Echinodermata. The Medusae attach themselves by these sucking-disks to the 

 vertical walls of the glass vessel, and climb up them like an Asterias or a Sea-urchin 



