io8 The Ottawa Naturalist. [Ju1>^ 



n size, from that of a pea, to several feet in diameter [a speci- 

 men measuring one foot in diameter was found in Patterson's 

 Creek just above Elgin St. bridge.] Each individual of a 

 colony is called a Polypide. It is a very beautiful object under 

 the microscope, most delicate in structure and transparent. 

 Whenever disturbed the polypide retracts quickly into its case 

 or ccenoecrum. Altogether it forms one of the most interesting 

 classes of objects formed in fresh water. 



Fresh-water Polyzoa are very generally distributed in the 

 ponds and slow-moving streams, and lake shores above Ottawa, 

 and the wonder is that their beauty has not long ago been found 

 out. No systematic study of the Fresh-water Polyzoa has as 

 yet been m.ade in this district. 



Br A. C. fitockes in his "Aquatic Microscopy" p. 237 

 makes the following statement. " Their beauty is so exquisite, so 

 delicate, so refined in its comeliness and grace, that no descrip- 

 tion could be too extravagant when applied to the charming little 

 creatures. Nature was never in a better mood than when she 

 began the developement of the Polyzoa, so she fashioned them 

 with care." 



Seven genera of Fresh-water Polyzoa have been iound and 

 described in the United States of America, as follows : — 



Plumatella, Fredericella, Paludicella, Cristatella, Pectina- 

 tella, Urnatella, Lophopus. 



In America, Lophopus has only been recorded from two 

 localities having been fi)und in California, and at Trenton, N. J. 



Polyzoa are usually found attached to some submerged 

 object, a piece of board, weed, stump or stone. An exception 

 to this is the species referred to, Cristatella, which moves more or 

 less slowly from place to place. 



Young zooids after leaving the egg swim freely for a short 

 time, and then become attached to some object, to which they 

 then adhere till death. Certain forms prefer the sunlight while 

 others are only found in shady places and others still, thrive on 

 the under or dark side of sticks, boards or stones. 



Decription of species found at Ottawa. 



