426 DR. S. F. HARMER ON THE 



33. The Polyzoa * of Waterworks. 

 By Sidney F. Hakmek, Sc.D., F.R.S., F.Z.S.f 



[Received March 11, 1913: Read April 22, 1913.] 

 (Plates LXII. & LXIII.J) 



Index. 



Bionomics : Page 



Relation of Polj'zoa to the other Constituents of the Fauna and Flora... 428 



Economic importance of Pol3'zoa 426 



Records of occurrence of Polyzoa in British Waterworks 435 



Sj'stematic : 



PaludiceUa ariiculata 441 



Fredericella sultana 448 



JPlwnatellafimgosa, var. eoralloides 449 



Flumatella emarginata, var. muscosa 452 



Development of hibernacula oi Fjludicella 444 



Morphology of hibernacula and statoblasts 446 



I, Historical Account. 



It is perhaps not generally recognized in this country that, 

 nnder certain circumstances, Polyzoa may be of great economic 

 importance. But it has long been known to those interested in 

 the subject, particularly in Germany, Holland, Belgium, and the 

 United States, that a group of organisms, among which certain 

 Polyzoa play a leading part, may flourish in the pipes of water- 

 works which are not provided with an efficient filtering apparatus, 

 to such an extent as to give rise to the most serious inconvenience, 

 and may indeed finally throw the whole system out of gear. It 

 is the object of this paper to show, by means of examples which 

 have come under my notice during the last two or three years, 

 that this coiintry is by no means exempt from the risks which 

 have been experienced in various places abroad. 



The first important contribution to the subject was an ex- 

 tremely interesting paper by Kraepelin (85), published under the 

 title of " Die Fauna der Hamburger Wasserleitung" ; although, 

 as Kraepelin himself points out, a list of 18 species of animals 

 from the pipes of the same water-supply had been published 

 by Petersen some nine years earlier. The occurrence of such 

 organisms as Asellus and Gammarus in the water supplied to 

 houses in Hamburg was no rare event in that city ; while the 

 pipes were frequently choked by Eels, " Leitungsmoos " and 

 other organisms. Kraepelin undertook a biological investigation 

 of the subject, influenced partly by the hope of finding blind 

 Crustacea among the inhabitants of the water-pipes, to which 



* [In view of the difference of opinion as to whether this Phylum should be called 

 Polyzoa or Bryozoa (see Proc. Linn. Soc. 1911, p. 61), I have accepted the preference 

 of the author. — Editoe.] 



f Published by permission of the Trustees of the British Museum. 



J For explanation of the Plates see p. 456. 



