FIELD BOOK OF PONDS AND STREAMS 



walls of reservoirs and hang from twigs and water plants. 

 They become covered with algae and look like green grape- 

 fruit. Each rosette-like cluster constitutes one group. The 

 central jelly mass is made larger as the number of animals 

 increases. Toward fall thousands of statoblasts form, and are 

 gradually washed from the jelly surface as the colonies die. 

 They are banded by air-filled cushions and armed with a 

 single row of hooks which catch upon everything with which 

 they come in contact. They float like life-preservers on the 

 surface, and are often piled up in thin brown streaks along 

 the shore line. 



Occurrence. — Common. Northeastern states to Illinois and 

 Michigan. August-October. 



Fig. io8. — Cristatella miicedo: i, coiony; 2, 

 statoblast. 



Cristatella mucedo. — Colony oval, rug-like, i to 2 inches 

 long on the undersides of leaves, especially lily pads (Fig. 108). 

 Toward autumn they grow longer and one colony may be 

 fused with another, giving the effect of a winding, branching 

 mat. When collected the animals will begin to wave their 

 tentacles as soon as the water is quiet; looking down upon 

 their hundreds of waving tentacles is like peering into mini- 

 ature gardens of translucent flowers. 



Occurrence. — In quiet waters. Northeastern states and 

 Canada to Illinois. Common in Massachusetts. May- 

 August. 



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