420 
MR. T. H. HUXLEY ON THE ANATOMY OF THE MEDUSA. 
pi-olongations of these membranes ; they are therefore do able- walled, and contain a 
cavity continuous with that of the canal. At their upper part they are thicker than 
below, where their outer membrane is developed into spherical processes containing 
multitudes of thread-cells and closely resembling those on the generative membrane 
(30.). The inner cavity becomes obliterated at the lower part of the tentacle, 
fig. 19. 
36. The large interbrachial tentacles of Cephea are processes of the branched 
arms. For the greater part of their length they have the same structure as the arms, 
i. e. consist of a dense, thick, transparent outer substance and an inner membranous 
wall inclosing a tubular canal ; but at the extremity they are thickened, and the outer 
wall is raised into a number of small pyriform processes, x^^th of an inch in diameter, 
thickly covered with minute spherical thread-cells, of an inch in diam.eter. At 
the same time the central canal becomes branched out into a kind of plexus, which 
occupies the interior of the enlarged end of the tentacle, fig. 37- These tentacles 
are 2 inches or more in length and ^^th of an inch in thickness, but other smaller 
tentacles, fths of an inch in length by -^th of an inch in diameter, depended from 
the arched concavity of the brachiferous plate. Their general structure much re- 
sembled that of the foregoing, except that the central canal terminated in a blind 
simple extremity, and that the pyriform bodies extended rather further up the stem. 
Beside these there was a third small kind of tentacles, which appeared as small 
blue points among the stomachs. These were clavate bodies placed without any re- 
gular order in the axils between the stomachs, and containing an internal cavity 
which communicated with the nearest branch of the common canal. A series of pyri- 
form processes, exactly resembling in form those above described, was arranged round 
their hemispherical extremities. As the individual I observed was a young one (the 
generative organs not being developed), I conclude that these were young forms of 
the longer tentacles, fig. 36. 
37 . Of the Generative Organs. — It has been already noticed with regard to the 
Cryptocarpae by Will (in Geryonia, Thaumantias, Cytceis, Polyxenia), and by Milne- 
Edwards (in .SLquorea), that the generative organs are connected with some part of 
the system of canals, but they do not attempt to define the nature of this connection. 
I shall endeavour to do this, and to show that the generative organs, both in these 
and in the Phanerocarpse and Rhizostomidee, are always portions more or less deve- 
loped of the wall of this system ; and therefore consist of the two “foundation mem- 
branes,” in or between which the generative elements, whether ova or spermatozoa, 
are developed. 
38. In Thaumantias there are four canals radiating from the centre of the disc, 
at right angles to one another, and terminating in a circular vessel at the edge of the 
disc. Near its termination each has a rounded body seated upon it. In most of the 
specimens I examined this body was distended with ova, and its structure was thereby 
obscured ; but in one instance it was replaced by an elongated, somewhat pyriform 
