ON THE GENUS LUCERNARIA, 269 
regular angles or points (s), the apices of which are attached to 
the gelatinous disc. This attachment is continued im a line 
(r) almost to the margin of the goblet, and, by the four 
lines of connection produced in this manner between the 
gelatinous disc and the natatory sac, the internal cavity is 
divided into four spaces (r)—radial vessels—which only com- 
municate with each other round the margin of the cup. These 
bands of connection are much broader in L. octoradiata than 
in L. campanulata, being in the latter almost linear, while 
they may rather be termed bandsin the former. They always 
run opposite the sides of the more or less quadrangular oral 
tube, and at the point of each angle of the swimming sac, 
they meet the strap-shaped generative organs. In those 
species, also, in which the dise is divided into four arms, as 
in L. guadricornis, these lines of connection le in the middle 
of each arm, and, consequently, if the groups of tentacles 
placed within the space of one expanded radial canal are to 
be regarded as belonging to one and the same set, in the 
case of these four armed cups, the two groups at the extre- 
mity of each arm do not belong to the same set, but are 
constituted of contiguous groups belonging to two distinct 
arms. 
The connection of the gelatinous disc with the natatory 
sac, and the lines of junction of the two, may be most easily 
seen in a transverse section, made either in a radial direc- 
tion through both walls (fig.3), or m a circular one around 
the cup (fig. 2). 
In the outer membrane of the gelatinous disc, as well as 
in that of the natatory sac, numerous thread-ceils are 
lodged, which, as is always the case, are produced in the 
cells of the membrane. On the outer surface of the disc 
they form spots of about 0:-1—O:2 mm. in diameter, in which 
the outer membrane is somewhat tuberculated, and contains 
the oval thread-cells (0-011 mm. long), which are arranged 
side by side, like palisades, together with yellowish pigment- 
granules, which give a reddish colour to the whole surface. 
These coloured collections of thread-cells do not often 
occur on the surface of the natatory sac, but in this situation 
they are lodged in great numbers in follicles of the outer 
membrane (fig. 14). These form the round, white, or, in 
L. campanulata, often turquoise-blue spots (7), visible to the 
naked eye, and already mentioned by Lamoureux, and which 
abound especially round the margin of the cup and along 
the course of the generative organs. These follicles are 
simple depressions of the outer membrane, 0°18 — 0:22 mm. 
in diameter, which consequently project into the internal 
