THE MICROSCOPE. 259 
As Cristatella is a collection of sentient animals, a colony of 
creatures living permanently immersed within the jelly which 
their own bodies secrete, there arises an interesting query, prob- 
ably impossible of solution at present, as to the method by 
which the selection of the route to be pursued is determined. 
They must necessarily be of the same mind, for rebellion at the 
extremities would result in a motionless existence, for a time at 
Jeast, and a revolt in the centre would only entail a somewhat 
greater pulling strain on the front rows, and a little more push- 
ing force at the rear. Even if the selection be left to the front 
or to the rear, how does the front or the rear transmit the de- 
cision? However, Cristatella is the travelling Polyzoan colony, 
and the only one. The others are all sedentary except when 
accidentally broken from their attachment. 
Lophopus is described as a colorless, sac-like jelly-mass vary- 
ing from one-tenth to one-half inch in diameter, and usually 
branching, especially when mature or old. Itis found attached 
to the leaflets of the Duckmeat (Lemna), and is, as already 
stated, restricted to European waters. 
There is another section of the Polyzoa, including those that 
live in social colonies, but which secrete long chitinous tubules 
-in which they dwell. These tubules 
soon become brown if they are not so 
from the first, and they are more or less 
conspicuous objects on the under sur- 
face of submerged stones, floating logs, 
and similar supports. They form clus- 
ters of variously curved and twisted 
and branching tubules which, in some 
genera, are adherent for their whole me cepa ee 
length to the supporting object, while A—Annulus. 
in others the branches are free to float in the currents while only 
the main portions of the domiciliary tubules are permanently 
adherent. 
The members of another beautiful genus consist of a flexible 
sometimes branching cluster of urn-shaped cells, as if little vases 
were piled one on the other. The colony is attached only at the 
“base, the remainder of the series of urns floating freely in the 
-water, the animal protruding itself from the orifice of the ter- 
minal one. It is found in running water, attached to the lower 
surface of stones and rocks from which it hangs downward. 
