* OR FRESH-WATER POLYZOA. 59 
although situated outside of the mouth (fig. 5,1’), it seems 
to answer many of the ordinary purposes of a tongue. 
It evidently discriminates between the different kinds 
of food, but is oftener employed to close the mouth 
over some struggling animalcule which obstinately refu- 
ses to be swallowed. It is a fleshy semicircular promi- 
nence formed by a fold of the disc (fig. 5, I), and is both | 
the door of a trap, and an organ of taste combined. 
The crown is interesting, not only on account of its 
beauty, and delicate transparency, but from the dreamy 
outline of each little thread, caused by the movements of 
the innumerable hairs investing them. The hairs, or cilia, 
themselves, are not visible, owing to their extreme ten- 
uity, but the waves they make in the water can be plainly 
seen. So many thousands of these cilia are simultaneously 
moving upward on the outer sides of the threads, and 
downward upon their inner sides, that they force the 
water along in strong currents from the exterior down 
toward the bottom of the open-work vase where the mouth 
lies. The meeting of these currents coming from all sides 
at once, creates a whirlpool, in which hundreds of care- 
less animalcules are continually caught and transported to 
the mouth. This being placed at the centre of the vortex 
catches all the objects entrapped by the current above, 
and it has, also, unfortunately for its helpless prey, a 
stomach beneath, which is indeed “an abyss no riches can ` 
fill.” The thousands of sleepless cilia are day and night 
constantly in motion, drawing into the throat an endless 
stream of food. The stomach below is equally active, and 
thus all the organs work harmoniously, like machinery 
driven by steam, untiringly capturing and digesting the 
food, which, when assimilated, supplies the waste occa- 
sioned by the great activity of these parts. The threads 
