SYNOPSES OF NORTH-AMERICAN 
INVERTEBRATES. 
I. FRESH-WATER BRYOZOA. 
C. B. DAVENPORT. 
THESE minute animals are found very abundantly in ponds 
and streams. Upon the underside of floating boards or of 
fallen tree trunks, in quiet pools or ponds, one may find the 
branching Plumatellas and Fredericella; upon rocks one often 
finds the P/umatella punctata in crowded masses. In pond- 
bottoms or in slow-moving streams Cristatella may be found on 
leaves of aquatic plants or bottom débris. More rapid streams 
afford Paludicella and Pottsiella. Below milldams, where the 
waters are turbulent, Urnatella and Pottsiella have been found 
together on stones. In reservoirs near where the waters are 
being pumped in, or on the gates of milldams, one may look for 
Pectinatella. _ Since all species form colonies by budding, com- 
pounds of Bryozoa may be formed of great size. Some of the 
Plumatella colonies stretch over a plain surface six inches in 
diameter, and a Pectinatella colony may become by the end of 
summer a sphere two feet or more in diameter. Bryozoa prefer 
the shade, and hence are more apt to occur in places not directly 
illumined by the sun’s rays. 
Fresh-water Bryozoa pass the winter in an inactive stage. 
The Phylactolemata produce little seed-like bodies called stato- 
blasts. These may be found as minute brown bodies floating 
on the surface of ponds in the winter and spring. If some of 
these are brought indoors in the early spring, they will hatch 
out after a few days, revealing a double embryo, which is one 
of the most beautiful objects for microscopic observation. The 
food of fresh-water Bryozoa consists of minute plants suspended 
in the water, such as diatoms. 
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