952 



FRESH-WATER BIOLOGY 



5 (4) Stock composed of zooids that are sharply separated from one another 

 by partitions; sparsely, usually oppositely branched; with 

 a chitinous cuticula. The zooids are club-shaped and have 

 a lateral, quadrangular aperture near the larger, distal end. 

 Paludicella ehrenbergii van Beneden 1848. 



p \ Zooids about 2 mm. long; lateral buds partly repent, 



partly erect; about 16 tentacles. Habitat, flowing streams; 

 a occasionally in water pipes. From Massachusetts, Penn- 



sylvania, Illinois, and Lake Michigan. 



FIG. 1396. Paludicella ehrenbergii. (a) Colony, half natural size. 

 (b) Portion of same enlarged. X 5- (After Kraepelin.) 



6 (3) Zooecia confluent; epistome present. . Order Phylactolaemata. . 7 



7 (14, 15) Statoblasts without hooks, rounded at ends. . 8 



8 (9) Stock branched in form of antlers; more rarely massed with recumbent 



and elevated tubes; mostly brown or incrusted with algae 

 and grains of sand; rarely hyaline. 



Fredericella sultana Blumenbach 1774. 



Tubes cylindrical, the older ones mostly keeled. 

 Without complete dissepiments. Apertures terminal 

 at the broadened or bifid ends of tubes. Polypide 

 very long and slender; tentacles arranged in a nearly 

 circular corona. Few tentacles, not exceeding 24. 

 Statoblasts dark brown, bean-shaped or elliptical, 

 without float, and with smooth upper surface. 

 Habitat on wood, stones and water plants ki standing 

 and slowly flowing waters. From Maine to Penn- 

 sylvania, westward to Wisconsin and even Flathead 

 Lake, Montana. Common in the Great Lakes. 



Fredericella sultana, (a) Portion of branch, 

 natural size, (b) Polyp magnified. (After Hyatt.) (c) 

 Statoblast. (After Kraepelin.) 



FIG. 1397. 

 ral i 



9 (8) Colonies consist of cylindrical tubes, which are either branched or form 

 massive clumps or run over the substratum as hyaline, 



lobed tubes Plumalella Lamarck. . 10 



Partitions rudimentary or absent, cuticula brown to hyaline, often incrusted. Tentacular 

 corona markedly horseshoe-shaped, with 40 to 60 tentacles. Intertentacular membrane present. 

 Statoblasts without hooks; either free, elliptical, with broad float, or (in the horizontal tubes) 

 without float, of large size and irregular shape. 



The commonest genus of our fresh-water Bryozoa. Has'been reported from all continents ex- 

 cept Africa. Lives in the most diverse habitats, in ponds or streams, usually not in the light. 



10 (13) Colony with vertical as well as horizontal branches n 



