274 ON THE GENUS LUCERNARIA. 
some solid discoid bodies in the wall of this oral tube in L. 
campanulata, which serve for the crushing of the food, but 
I have not been able to find these myself. 
In this stomach the digestion of the nutriment, consisting, 
as all observers agree, of small crustaceze and molluscs, is 
effected. I have never noticed any trace of food in the stem, 
or radial canals, although Sars has found some in the latter 
situation. 
Numerous vermiform internal oral tentacles are set in a row 
on the margins of each point of the natatory sac, and which 
commonly project into the cavity of the stomach, where they 
move about in a serpentine manner. In the Meduse these 
internal oral tentacles are very large, and one cannot help 
ascribing to them some function in the digestive process. 
It can be demonstrated with certainty in Lucernaria, as Fritz 
Miiller has already described in Meduse, that these tentacles 
are solid within, and consist of the gelatinous substance, 
covered by the outer formative membrane, and we cannot, 
therefore, agree with Gegenbaur, who, in Medusa, nor with 
Frey and Leuckart, who say that in Lucernarva these tentacles 
are hollow. Many oval thread-cells are imbedded in this 
membrane, and it is everywhere furnished with cilia, which 
exist also throughout the whole gastric cavity. 
These internal oral tentacles have a peculiar structure in 
L. campanulata (figs. 16, 17), the outer membrane being 
much thickened throughout two thirds of the circumference, 
and forming nodular projections on the internal aspect. This 
larger portion of the tentacles contains no thread-cells, 
which occur only in the narrow tracts, where the outer mem- 
brane is of its usual thickness, and has a smooth surface 
towards the interior. 
7. The gastro-vascular system.—As parts of the gastro- 
vascular system in Lucernaria must be reckoned the cavity 
of the stem, and that between the gelatinous dise and the 
natatory sac in the sides of the bell. I cannot positively 
assert whether these cavities are shut off from that of the 
stomach at the time of digestion, but it seems, nevertheless, 
very probable, and when food is found in them it may be 
assumed to have entered there by accident. 
The whole gastro-vascular system is clothed inside with 
delicate cilia (fig. 9), springing from the cuticle by which the 
cellular layer of the inner membrane is covered. 
The cavity between the double walls of the bell is divided 
by the four lines of connection between the outer and inner 
membranes (7) into four spaces (x) answering to the four 
