ostenfeld: the piiytoplankton of victoria nyanza. 181 



but is probably a warm-water form. An analogous phenomenon is that 

 Coelastrum Stuhhnanni, described by W. Schmidle (Botan. Zentralblatt, 

 1900, 81 ; Engler, Botan. Jahrb., 1902, 32, pi. 3, fig. 8) from Victoria 

 Nyanza, occurred also in Lago di Muzzano, and through all intermediate 

 stages was connected with C. cambricum Archer, of which it is to be 

 considered as merely a variety. The main character in C. Stuhhnanni 

 is the prominent ribs radiating from the external tips of one cell to the 

 tips of another ; in Lago di Muzzano some coenobia without these radiat- 

 ing ribs were found, others with radiating ribs on some of the cells, and 

 others again which were true G. Stuhhnanni. Already in my paper 

 (I. c, p. 337) I had suggested that C. Stuhlmanni was nearly related to C. 

 cambricum, var. elegans C. Schroeter, and this has now proved to be the 

 case ; but perhaps we may retain the form as a variety, viz., C. cambricum, 

 var. Stuhhnanni (Schmidle) Ostf. In this way one more of the endemic 

 forms for Victoria Nyanza has disappeared. 



