1907.] OF THE THIRD TANGANYIKA EXPEDITION. 251 



water si3onge, Spongilla tcmganyikce Evans, only the small heads 

 projectuig beyond the surface of the sponge. Its affinities appear 

 to approach nearest to Victorella, and I have therefore named it 

 Victorellcf, sijmbiotica . 



The following is a list of the five species here described : 



1. Plumatella tanganyikce^ sp. n. 



2. ,, o^ejjens, var. ? 



3. Fredericella cunningtoni, sp. n. 



4. Arachnoidia o^ay-lankesteri Moore. 



5. Victorella symbiotica, sp. n. 



The number of known species of Polyzoa inhabiting African 

 fresh waters is thus brought up to eight, truly a remarkably 

 small number for this vast continent. 



The other African species so far recorded are the following : 



Fredericella sultana, found by Dr. Stuhlmann in Alexandria, 

 Egypt (7), and in the Equefa River, Natal, by the 

 Hon. Thos. Kirkman *. 

 Plumatella rejmis, var., from Ugogo, Victoria Nyanza, Albert 

 Edward Nyanza, and Albert Nyanza : the statoblasts only 

 found by Dr. Stuhlmann (7) and also by Dr. Meissner 

 on shells of uEtheria (in the Berlin Museum) from the 

 Upper Nile, White Nile, the Niger, and Senegal (8, 9) 

 Lopliopodella {Pectinatella) carteri Hyatt, from JJgo^o- 



statoblasts found by Dr. Stuhlmann (7). * 



Lophopodella thomasi liouss., from Hunyani River Rho- 

 desia (12). ' 



The indifferent preservation of the Tanganyika specimens has 

 unfortunately hampered and prevented a complete study of all 

 the species. They were narcotised with cocaine and then pre- 

 served m alcohol, which is not a sufficiently good fixative for 

 these annuals. Freshwater Polyzoa must not be allowed to die 

 m the anaesthetic, which quickly macerates their delicate bodies 

 After treatment with cocaine in perfectly clean water they should 

 be killed and fixed whilst still living, either with very weak 

 osmic acid {-^ per cent.) for ten minutes to half an hour, accordino- 

 to the age and actual strength of the solution, then washed and 

 also preserved, in 3 per cent, commercial formalin (97 c c water 

 3 c.c. formalin) ; or else fixed with a 10 per cent, solution of 

 formalin (90 c.c. water, 10 c.c. formalin) for 24 hours then 

 preserved in 3 per cent, formalin to which A per cent, glycerine 

 maybe added to render the animals more transparent. Polyzoa 

 fixed with osmic acid are stained brown, or even black, if allowed 

 to stay too long ni the fixative ; those fixed with formalin remain 

 white and transparent. 



The little bottles in which the preserved specimens are stored 

 should have no air-space ; an air-bubble plays havoc with the 

 delicate tentacles of extended polypides. 



* Mentioned in his paper on the Rotifera of Natal as supporting tubes oi Limnias 

 eeratopliylli : Journ. Roy. Micr. Soc. 1901, p. 232. ^^mnias 



