OR FRESH WATER POLYZOA. 135 
The eggs eventually attain the size of a statoblast 
(about one-thirtieth of an inch long), and have an oval 
outline. When full grown, their exterior is also clothed 
with cilia, which render them capable of rapid motion, 
and at this period they may be sometimes seen squirming 
in the tube, and tossing the stomach about with great 
violence. No orifice for their emission from the body 
has been discovered, and we have every reason to believe 
there is none, and that they force their way into the 
world directly through the walls of the body. In fact, 
Mr. Albany Hancock, an English naturalist, has observed 
a full-grown egg, which obtained its liberty by press- 
ing through the closed orifice of the cell, rending and 
destroying the parent in its course. 
The cceneecia, composing the trunks of the older colo- 
nies, are always empty, as previously stated, in the au- 
tumn, and it is not improbable that they are the remains 
of the unfortunate parents whose death was caused earlier 
in the season by their restless offspring, since all, even 
the younger autumnal polyzoa are incapable of bringing 
forth eggs, and produce only statoblasts and regular 
buds. 
The polyzoén is developed from an internal bud at one 
end of the egg, and when sufficiently large bursts the 
outer envelope, coming forth like the polyzoén of the 
statoblast, armed with abundant cilia, by whose aid it 
swims. Like this, also, after a time its wandering ceases ; 
it seeks some dismal retreat, glues itself to the surface, 
and becomes the progenitor of a new colony. 
All Polyzoa, both marine and fresh water, in common 
with other attached and branching forms, such as the 
corals among the Radiata, have been called Phytozoa, or 
