250 Records of the Indian Museum. [ Vou. VII, 
or rejected, while the little teeth with which they are provided 
assist in its retention. 
When Caridinicola is undisturbed in the gill-chamber of its 
host it habitually remains with its body in a state of moderate 
retraction, approximately as in fig.2d. The posterior sucker is 
firmly fixed toa gill-filament and the body is arched upwards and 
forwards in such a way that the c-ves look directly forwards and 
outwards, the anterior extremity being bent considerably down- 
wards. If any disturbance occurs, however, the animal imme- 
diately straightens itself and elongates its body to the utmost. 
Such attitudes as those shown in fig. 2a and b are only adopted 
just before it begins to move forwards. Apparently the rule that 
it emerges from the anterior end of the gill-chamber is absolute, 
and it invariably escapes vid the antenna or antennule. As soon as 
it reaches the filamentous part of one of these appendages it stays 
its course and remains for some little time with the peculiar 
posterior sucker clasped round the hair like structure. The body 
is stretched to the utmost and moves rapidly upwards and down- 
wards and from side to side, often gyrating almost as if on a pivot; 
but the sucker retains a firm hold. ‘The tentacles during these 
evolutions exhibit curious twitching movements apparently neither 
correlated in the case of the two tentacles nor rhythmical. At 
length the Caridinicola releases hold of its host and drops to the 
bottom or onto a convenient weed. It seems probable that it 
habitually deserts its host at night, for I found it difficult to pro- 
cure specimens on Caridina in the Mahanaddi early in the morning. 
Progression is effected by means of “‘looping.” The body is 
first held upright and stretched to the greatest possible length. The 
anterior extremity is then bent downwards and the surface along 
which progression is to be effected touched gently by the tentacles 
with their characteristic twitching movements. ‘The two little 
anterior suckers next take hold, and the posterior sucker is released, 
drawn forward to a position immediately behind that occupied by 
them and then affixed again. ‘The animal is now in readiness for 
a new move forwards. 
Taking the above-stated observations into consideration, it 
seems probable that the tentacles are, as their structure would 
suggest, primarily of use as sensory organs. ‘They seem to play 
no other part in progression than that of testing the ground before 
the anterior suckers attach themselves to it. They have, I think, 
another function, namely that of finding the right host. I noticed 
that if a Caridintcola were removed from its host and placed ina 
dish of water in which a Caridina of the right species was present, 
it immediately stood up in the water on its posterior extremity 
and, after twisting about in all directions and flicking its tentacles, 
finally directed them in the direction of the Carvidina and then 
moved rapidly towards it. This happened whether the Caridina 
was dead or alive; indeed, even if it were torn in pieces, the little 
worm appeared to be attracted by the fragments and attached 
itself to one of them. 
