1912. | Records of the Indian Museum. 255 
also much longer than the secondary ones. They extend upwards 
from the base through the jelly of the bell for a short distance and 
on emergence therefrom lie parallel to its external surface, each in 
a shallow groove, for about twice the distance for which they are 
enclosed in the jelly. This groove extends to the edge of the 
umbrella. On its termination the tentacle bends outwards and 
upwards and then downwards. At the point at which it does so 
there is only a very slight prominence on the surface of the 
umbrella. The base of the primary tentacle is both constricted 
from side to side and flattened dorso-ventrally. On the dorsal 
surface, where it is in contact with the mesogloea below the 
ectoderm vf the bell, its endoderm contains numerous small poly- 
gonal cells of a yellowish colour due to their thickened walls. 
The secondary tentacles are not only much shorter but also 
more nearly cylindrical and equal than the primary ones. ‘They 
project practically straight out from their base, which is not, or 
only to a very slight extent, enclosed in the jelly. 
The full number of tentacles is 384. Every primary tentacle 
is followed by five secondary ones arranged in a straight line with 
their bases a little further from the velum.! There are thus 64 
series of six tentacles each, each consisting of one primary and five 
secondary tentacles. The radial tentacles are followed by five 
secondary tentacles just as other primary tentacles are. 
It might be possible to divide the primary tentacles into several 
series by their length and in the adult medusa the radials are 
distinctly longer than the others ; but the differences in this respect 
are slight and apparently unimportant. In the young medusa 
1°75 mm. in diameter only two series can be distinguished and the 
radial tentacles are very little if at all longer than the others. At 
this stage there are 24 primary tentacles and each is followed by 
a single secondary one, which is distinguished not only by its 
smaller size but also by being placed a little lower on the edge of 
the bell as seen from the side or above. 
Sense-organs.—The otocysts are comparatively large, at least 
equallying the base of the largest tentacles in diameter. They 
also have avery definite arrangement in the adult. Every set 
of five secondary tentacles has two otocysts at its base and these 
two are separated from the next pair by the base of a primary 
tentacle and by an outward emargination of the inner edge of the 
ring of thickened tissue at the base of the tentacles. It is always 
quite clear, in well-preserved specimens, that the otocysts are not 
situated at the base of the primary tentacles and are not sur- 
rounded by anything like a tentacular bulb. In the young medu- 
sa already alluded to there are only three fully formed otocysts in 
each quadrant, 7.c., only twelve in all ; while in an older medusa 
measuring 3°25 mm. in diameter there are five in each quadrant. 
1 Owing to the fact that the base of the primary tentacle is embedded in 
the jelly, this tentacle, unless a very careful examination is made from below, has 
the appearance of arising further from the velum than the secondary tentacle. 
