54 Records of the Indian Museum. [Vo.. XII, 
cell appears to contain a single vacuole, so large that the proto- 
plasm is reduced to a delicate peripheral layer in which nuclei 
are scareely visible. Except for the granular contents of the gut 
cavity the stalk is transparent. The appearance of transverse 
lines in it is due to protoplasmic septa composed of the peripheral 
layers of adjacent endoderm cells which separate the vacuoles. 
Since the diameter of the hydrotheca is not much more than 
twice the diameter of the extended stalk, it is evident that the 
~ cubic content of the stalk must be very much reduced before it 
can be accommodated by the hydrotheca during contraction. 
This reduction must be brought about by evacuation of fluid from 
the vacuoles of the endoderm cells, The process however was not 
observed. As mentioned before, the endoderm cells of the stalk 
present a very different appearance from those of the stolon and 
intermediate branches, the latter being granular and not vacuo- 
lated. The transition from the one to the other issudden. When 
extended the stalk is straight and stiff. It usually appears to be 
motionless but on attempting to draw the outline with the Camera 
lucida, it becomes evident that the animal is seldom quite motion- 
less. In the largest individuals the tentacles are constantly six- 
teen in number. When extended they measure about ‘5 mm. in 
length and they are usually held in two series, eight of them 
springing from the base of the hypostome at an angle somewhat 
less than a right angle, while the other eight which alternate with 
them project more downwards. When the tentacles are in this 
position the margin of the web forms a characteristic zig-zag out- 
line. The web measures about ‘06 mm. from its margin to the 
angle between adjacent tentacles The tentacles are as usual in 
the Calyptoplastica devoid of a central cavity, the outline between 
the endoderm cells being plainly visible in the living animal. 
That part of the base of the tentacles which lies in the web usually 
includes three endoderm cells and bears a few scattered nemato- 
cysts. Throughout the length of the tentacles the nematocysts 
are disposed somewhat irregularly in rings, one ring corresponding 
roughly to each endoderm cell. 
Habits. 
The hydroid first found at Port Canning was living in as- 
sociation with the protozoon Folliculina and this organism also 
occurred among the colonies taken from the canal. A species of 
small Polychaet worm (Spioniformia), however, was found more 
plentifully in association with the hydroid at Calcutta. The deli- 
cate sandy tube of the Polychaet was frequently interwoven with 
the stolon of the hydroid. On one occasion I was able to observe 
the hydroid preying upon the worm. ‘Three fully expanded hy- 
droids which happened to be adjacent were under observation in a 
capsule of water. An immature worm measuring about a milli- 
metre in length came within reach of their tentacies and was soon 
fast entangled and paralysed. One hydroid attached itself to the 
mouth of the worm another to the anus, while the third which 
