170 MR. С. 5. WEST ON THE FRESHWATER ALG.E 
however, says that ihe € yellow clouds” consisted of a large infusorian 
resembling а Peridinium ог а Colpodium. The organism in question may 
have been a Peridinium or possibly Botryococcus Braunii, a Protococcaceous 
alga, which is the cause of similar coloration and * yellow clouds " in many 
European lakes. 
Var. CIRCULARIS, var. п. (Pl. 4. figs. 10, 11, 14, 15 ; Pl. 10. fig. 2.) 
Var. filis brevissimis, spiraliter dispositis anfractibus 1-14, utroque fine 
heterocysta terminatis; cellulis spheericis, oblongo-ellipticis vel oblongis, cum 
granulo magno (gas-vac.) in cellula unaquaque. 
Crass. trich. 4:5—6 ш; crass. heterocyst. 5-8 д. 
Tanganyika.—In plankton, Komba Bay (11 Oct. 1904; no. 135), near 
Sumbu (13 Oct. 1904; по. 138), Vua Harbour (29 Oct. 1904 ; no. 150), 
near Kalambo (5 Nov. 1904; no. 154), near Kassanga (14 Nov. 1904: 
по. 159), near Chamaluki (15 Nov. 1904 : no. 160); near Kala (19 Nov. 
1904 ; no. 170), near Kirando (1 Dec. 1904 ; no. 175), near Maswa (14 Jan. 
1905 ; no. 211), and near Baraka (24 Feb. 1905 ; no. 240). 
This variety was the dominant feature of some of the plankton collections 
from Tanganyika, giving the collected sediment a decided blue-green colour. 
The trichomes are remarkable for their shortness, being mostly coiled in the 
form of a circle, sometimes overlapping at the extremities to form a spiral 
with about one and a half turns. Each end of this short trichome is 
terminated by a globular or ellipsoidal heterocyst, and both cells and hetero- 
cysts ¡contain a single large granule, most probably of the nature of a 
gas-vaeuole. The total length of the trichomes from heterocyst to hetero- 
cyst varies from -80 to 140 м. Very rarely a straight (or almost straight) 
trichome is observed among the coiled ones. The cells are somewhat variable 
in form, showing all gradations from globose to oblong. 
290. ANABAENA sp. (РІ. 9. fig. 8.) 
A. trichomatibus rectis rigidissimis, evaginatis, solitariis ; cellulis sphaerico- 
compressis, cytoplasmate atro-viridi et minute granulato;  heterocystis 
spheericis, diametro trichomatis subequalibus ; sporis non visis. Forsan sit 
propria species: A. rigidissima. 
Crass. trich. 11-12 д. 
Victoria Nyanza.—Among Utricularia, near Bukoba (20 Apr. 1905; 
no. 618). 
Tanganyika.—In plankton, near Kala (19 Nov. 1904 ; no. 170). 
The trichomes of this Anabena were remarkable for their exactly lineal 
character. 
291. PANABENA IN.EQUALIS, (Kütz.) Born. § Рай. in Ann. Sci. Nat. 
Г sér., Bot. vii. (1888) p. 231.—Spheerozyga inzequalis, Азис. (1843). 
Crass, trich. 3°5-4 u ; crass. heterocyst. 6 р; sporis non vidis. 
Муава. — [п swamp, Kambwelagoon near Karonga (27 Tune, 1904 ; no. 29). 
