46 C. F. ROUSSELET ON A NEW FRESH-WATER POLYZOON 



representative of fresh-water Polyzoa recorded from any part of 

 Africa south of the Equator. 



Before describing the characters of this new species, it may 

 be instructive to hark back a little and see what has been done 

 before, and what is the present state of our knowledge about 

 these animals. 



The fresh-water Polyzoa (or Bryozoa) form a very distinctive 

 group containing only about 20 to 50 species, according to 

 whether a number of these forms are considered good species, 

 or merel} 7 varieties, or synonyms. Professor G. J. Allman, who 

 in 1856 published his fine work, " A Monograph of the Fresh- 

 water Polyzoa," seems to have almost exhausted the subject as 

 far as Great Britain is concerned, for, with the exception of the 

 description of two very doubtful new Plumatellas by Parfitt (8) in 

 1866, and one remarkable new species, Kent's Victorella 

 jxwida * (9), from the Victoria Docks in 1870, no work at all, 

 or work of any importance, on this group seems to have been 

 done or published in England. The marine Polyzoa, on the other 

 hand, have come in for much more attention at the hands of 

 zoologists. 



During the last decades the principal descriptive work on fresh- 

 water Polyzoa has been done in America by J. Leidy (2, 11, 12) 

 and A. Hyatt (7), in Germany by Professor K. Kraepelin (17), 

 and Dr. M. Meissner (22, 23, 24, 25), in France by J. Jullien 

 (15), in Bohemia by Kafka (18), and in Japan by Oka (20). From 

 India, Japan, South America, Australia, and Indo-China a few 

 new species have been described, so that the total number of 

 undisputed species does not at present exceed 20, leaving out all 

 the more or less doubtful names w r hich have been alternately 

 accepted and rejected by different investigators. 



I will make no attempt to give even a short description of the 

 known species of fresh-water Polyzoa, which can readily be found 

 in the works mentioned in the bibliography at the end of this 

 paper ; but a bare list of the recognised species, and of those 

 named since Allman's monograph was published, may prove 

 useful for reference. 



* This was first found by Mr. W. Saville Kent at one of the earliest 

 Quekett excursions, on September 12th, 1868. See Mr. Kent's first note in 

 Science Gosaij) for 1868, p. 255. Later it has also been found in the 

 Regent's and Surrey Canals, always parasitic on Cordylophora laevstris. 



