POLYZOA. 303 
of branching tubes, occasionally a rounded mass of spongy appear- 
ance, and now as a flat lamelliform inarticulated expansion of cells. 
With some of the marine species the shell of the mussel is covered as 
with a fine lace. 
It is a remarkable fact that these cells are not always inert. They 
seem to enjoy some little power of motion. It is well known that 
the leaves and branches of the sensitive plant (dimosa) contract 
and expand under the touch of the finger ; the same phenomenon, 
according to Mr. Rymer Jones, takes place on touching the cells of 
certain species of Polyzoa. The moment they are touched they 
quickly incline themselves ; and the movement is immediately com- 
municated from one to the other, until all the cells of the community 
are in motion. 
Returning to the organisation of the little creature which occupies 
the cell, it is found that the upper and retractile portion, which is of 
extreme delicacy, terminates anteriorly in a circle of long tentacles, 
in the centre of which is the mouth. These tentacles are fringed 
laterally by a series of vibratile cilia. ‘‘When the animal displays 
‘itself,’ says Frédol, ‘‘this circle of microscopic threads of extreme 
tenuity first show themselves rising from the summit of the cell ; this 
is followed by the upper part of its body, which is more or less 
flexible ; the tentacles follow between the threads, pushing them cn 
one side.” 
These tentacles are furnished on the back with appendages like 
very fine hairs, attached to them nearly at right angles, in addition 
to the delicate cilia already spoken of, which play a very important 
part in the arrangements of most microscopic animals. At the 
moment when the tentacles appear outside the cell, the body of the 
animalcule, which has the power of expanding or contracting itself, is 
gradually unrolled. It soon spreads out its pretty little arms, the 
appendages and cilia beginning their rapid vibrations, until the eye, 
deceived by the rapidity and regularity of their movements, is 
dazzled, and the beholder begins to think that he sees rosy drops of 
dew waving to and fro, twisting and untwisting themselves. The 
corpuscles which float round the animal are violently agitated, as if 
they were under the influence of some strong breeze. Unhappy, 
indeed, is the fate of the unfortunate Infusorium which chance leads 
at this moment into the fatal circle. 
Darwin, who examined some of these creatures very minutely, 
tells us that “several genera (Flustra, Eschara, Cellaria, Cresia, and 
others) agree in having singular movable organs attached to their cells. 
The organs in the greater number of cases very closely resemble 
