CHAPTEE XVIII 



polyzoa (continued) 



FRESH - WATER POLYZOA PHYLACTOLAEMATA OCCURRENCE 



STRUCTURE OF CRISTATELLA DIVISION OF COLONY MOVE- 

 MENTS OF COLONY RETRACTION AND PROTRUSION OF POLY- 



PIDES IN POLYZOA STATOBLASTS TABLE FOR DETERMINATION 



OF GENERA OF FRESH-WATER POLYZOA REPRODUCTIVE PRO- 

 CESSES OF POLYZOA DEVELOPMENT AFFINITIES META- 

 MORPHOSIS BUDDING. 



Fresh- water PMyzoa. Although the Gymnolaemata are 

 ordinarily marine animals, fresh- water examples from this Order are 

 not altogether wanting. The Ctenostomata among the typically 

 marine groups show the most tendency to stray into fresh-water. 



Alcyonidium and Bowerbankia (Fig. 238) flourish in estuaries, 

 while Victor ella and Paludicella (Fig. 250) are only known as- 

 fresh or brackish water forms. Victor ella was named after the 

 Victoria Docks in London, where it was first found ; more recently 

 it has also been discovered in other parts of England and on the 

 Continent. 1 



The systematic position of the genera Hislopia and JVorodonia, 2 

 which have been described from fresh water of India and China 

 respectively, is at present uncertain. The undoubted Cheilostome 

 Mernbranipora has, however, a British representative (M. mono- 

 stachys), which occurs in brackish water, in ditches on the coast 

 of East Anglia. It is there known to form " friable, irregularly - 

 shaped, sponge-like masses," which grow on water-plants. 3 



1 Kraepelin, K., "Die deutschen Susswasser-Bryozoen." Abh. Ver. Hamburg, 

 x. 1887, No. 9, p. 95. 



2 Jullien, Bull. Soc. Zool. France, x. 1885, p. 92. 

 8 Hincks, Brit. Marine Polyzoa, i. p. 132. 



