OR FRESH WATER POLYZOA. 181 
extremely in the details of their anatomy and habits of 
lif 
e. 
The Plumatellæ abound near the shores of our ponds, 
close to the surface, and are generally found with Freder- 
icella. Better fitted, however, to endure thè sun’s rays, 
they sometimes seck places more exposed to their influ- 
ence, 
One sultry summer day, while searching for ac 
under the shelter of a bridge, my attention was drawn to 
the long water-grasses farther out in the stream, where, to 
my surprise, I found a specimen of Plumatella Arethusa, 
its tiny branches and living crystalline flowers glittering 
in the light as they Suiga in the current unprotected 
from Ni heat. 
The colony is like that of Fredericella, and in some 
Species the unpractised eye would not detect the differ- 
ence until the horseshoe-like dises were discovered. In 
others, however, such as Plumatella vitrea, the outer en- 
velope remains gelatinous and transparent in the adult as 
in the young, and the tubes, or polypides, are in groups 
of two and more, counting sometimes twenty plumes. 
The colony is dendritic, but the branches are always 
creepers along the surface, and there are no constrictions 
between the polypides, the branch being merely an elon- 
gated, undivided sac. It approximates, in this respect, to 
the next genus, Lophopus, and would belong to it, but 
that the statoblast has the plain, oval annulus of its com- 
patriots among the Plumatelle, which ranks it with them. 
Lophopus has, also, lobiform branches, but they are 
supported in an erect posture by the ectocyst, a lump of 
clear jelly in which they are buried. The whole colony 
is very minute, the polypides are all gathered at the ends 
of the branches, and no longer oceupy separate cells as in 
