134 MR. 6. $. WEST ON THE FRESHWATER ALGA 
Nyasa.—Plankton, Anchorage Bay (13 Apr. 1904 ; no. 9). 
Victoria Nyanza.—Near Bukoba (17 Apr. 1905; no. 248). In sheltered 
bay, near Entebbe (1 May, 1905 ; no. 620). 
Var. CLATHRATUM.—P. clathratum, (Schröt.) Lemm. Forschungsb. Biol. 
Stat. Plön, vii. (1899) p. 20 ; Sehmidle, in Engl. Bot. Jahrb. xxxii. (1903) 
t. 3. fig. 19. P. enoplon, W. $ G. S. West, in Trans. Linn. бос. ser. 2, 
Bot. v. (1895) p. 81, t. 5. figs. 1, 2. 
With large intercellular spaces between the central cells ; outer margins of 
peripheral cells typically concave. Processes long and moderately robust. 
Diam. coenob. 100-180 ш; diam. (max.) cell. 18-26 ш. (P1.2. figs. 17, 18; 
PI. 3. fig. 16.) 
Nyasa.—Plankton, off Vahambwera Point (24 June, 1904; no. 24) and off 
Karonga (1 July, 1904; no. 30). 
Victoria Nyanza.—Plankton, near Bukoba (21 Apr. 1905 ; no. 252). 
forma RADIANS.— P. simplex, var. radians, Lemm. 1897; Forschungsber. 
Biol. Stat. Plön, vii. (1899) р. 19, t. 2. figs. 24,25. P. simplex, В. annulatum, 
Chodat, 1902. 
Coenobium consisting of a ring of peripheral cells, the outer margins of 
which are concave; no central cells. 
Diam. ecenob. 46-75 ш. Ап abnormal ecenobium is figured on PI. 5. fig. 21. 
Nyasa.— Plankton, Anchorage Bay (11 and 13 June, 1904 ; поз. 5 and 9). 
Plankton, off Vahambwera Point (24 June, 1904 ; no. 24) and off Karongu 
(1 July, 1904 ; no. 30). 
Victoria Nyanza.—In sheltered bay, near Entebbe (1 May, 1905 ; no 620). 
forma MICROPORUM.—P. clathratum, var. microporum, Lemm. l с. 
р. 20, t. 2. figs. 20-31. P. clathratum, var. Baileyanum, Lemm. l.c. t. 2. 
figs. 26-28. 
Peripheral cells of cenobium as in typical var. clathratum; but central cells 
stouter with smaller intercellular spaces. 
Diam. ссепоћ. usque ad 182 y. 
Victoria Nyanza.—Plankton, near Bukoba (21 Apr. 1905 ; no. 252). 
—— forma ovATUM, (Lhrenb.).—P. Schróteri, Lemm. l. c. p. 20, t. 2. fig. 33, 
еі var. mieroporum, Lemm. t. 2. figs. 34, 85. P. clathratum, forma ovatum, 
(Ehrenb.) Schmidle, in Engl. Bot. Jahrb. xxxii. (1903) р. 84, t. 3. fig. 18. 
Central and peripheral cells ovoid and stout, margins generally convex 
(rarely slightly concave). 
Diam. coenob. usque ad 240 д. 
Nyasa.—Plankton, Anchorage Bay (13 and 14 June, 1904 ; nos. 9 and 10). 
Plankton, otf Vahambwera Point (24 June, 1904 ; no. 24) and off Karonga 
(1 July, 1904 ; no. 30). 
Victoria Nyanza.—Plankton, near Bukoba (21 Apr. 1905 ; no. 252). 
P. simpler occurred in great abundance in some of the plankton-material 
