Vol. 7 at 5.) Notes on the Freshwater Fauna of India. 193 
commensalism between marine Sponges and Hydrozoa, which are 
to some extent parallel to this bet tubicolous | and Spony 
carteri, the chitinous exoskeleton of the Coelenterates playing, how- 
art in the formation of the sponge 
/)92. valia 
fourth lives independently and fastens to its retreat Protozoa 
and other small animals on which it feeds. The habits of all these 
species tend, in greater or less degree, towards commensalism, and 
probably the one at present under consideration has gone further 
than the others in this respect. 
Tanypus sp. (larva). 
(2) the antenne can be completely retracted into cavities 
and the hind limbs can be entirely retracted, the latter being with- 
drawn into separate sheaths while the fore limbs disappear into a 
common tube which depends from the ventral surface of the first 
form a tu forces its way through the substance of the 
Sponge, pulling itself along by means of it~ conjoined fore limbs. 
ws its limbs and antenne into their 
cases and remains still, as if it were dead _ Probably it does not 
feed on the Sponge, but, like its ally found in the same organism, 
on minute animals which it catches by means of the hooks 
than is the Qhironomus, and I have taken a species prob- 
ably identical with it living free among water-weeds. It is 
colourless and apparently breathes by transmission of oxygen 
through the general. surface of its y, which is covered with 
a fine, softintegument It does not grow so big as the Chironomus 
larva. I have sometimes found a considerable number of 
