m 
OF THE THIRD TANGANYIKA EXPEDITION. 131 
also а small intercellular space between the four cells of each group. The 
abruptly truncate external angles of the cells are also peculiar. 
I have not seen any stage in the formation of auto-colonies in this species ; 
such a condition should be of great interest. 
153. C@LAstRUM RETICULATUM, (Dang.) Senn. — Hariotina reticulata, 
Dang. in Le Botaniste, 1. (1889) р. 162 : Chodat, Alg. Vert. Suisse, i. (1902) 
р. 233. C. subpulehrum, Lagerh. in La Nuova Notarisia (1893), p. 158; 
Bohlin, in Bih. К. Sv. Vet.- Akad. Handl. xxiii, (1897) no. 7, p. 37, t. 2. figs. 28- 
32. C. distans, W. В. Turn. in К. Sv. Vet.- Akad. Handl. xxv. (1893) no. 5, 
p. 161, t. 21. fig. 18. 
Diam. ecnob. usque ad 132 д. 
Nyasa.—In shore pools, Nkata Bay (23 June, 1904 ; no. 22). Plankton, 
off Vahambwera Point (24 June, 1904; no. 24) and in Deep Bay (24 June, 
1904 : по. 25). In swamp, Karonga (2 July. 1904 ; no. 88). 
Victoria Nyanza.—Plankton, near Bukoba (21 Apr. 1905; no. 252). 
Among Utricularia, near Entebbe (1 May, 1905 ; по. 620). 
Some of the specimens reached a large size, and the reticulate colonies were 
a conspicuous feature of the plankton. 
Genus SORASTRUM, Kütz. 
154. SonasrRUM Haruoris, (Cohn) Schmidle, in Engl. Bot. Jahrb. xxvii. 
(1899) p. 230; xxxii. (1903) p. 85.—Selenospherium Hathoris, Cohn, 
* Desm. Bongoenses, Festschr. zur Feier des hundertjihr. Bestehens der Natur/. 
Ges. in Halle-a-S. (1879) p. 13, t. 11. figs. 16, 17. 
Nyasa.—In swamp, Kota Kota (20 June, 1904 ; no. 18). 
Victoria Nyanza.— Plankton, near Bukoba (18 Apr. 1905 ; по. 249). 
Subfam. CRUCIGENIES, 
Genus CRUCIGENIA, Morren. 
155. CRUCIGENIA TETRACANTHA, sp. n. (РІ. 5. fig. 7.) 
Coenobium quadratum, e cellulis 4 formatum consociatum ; cellule sub- 
quadratz, lateribus subrectis, ad angulum exteriorum spina longa valida 
attenuata leviter curvata ornate, apicibus spinorum acutissimis ; pyrenoide 
singulo in cellula unaquaque. 
Diam. ecenob. sine acul. 17-19 ш; diam. cell. 9 ш; long. acul. 17-18 д. 
Tanganyika.— Plankton, near Baraka (24 Feb. 1905 ; no. 240). 
This species is, perhaps, nearest to C. heteracantha, Nordst., but 1s at once 
distinguished by the large solitary spine at the external angle of each of the 
four cells. It bears considerable resemblance to a four-celled colony of some 
forms of Pediastrum simplex. There is а minute space in the centre of the 
cenobium between the four cells, and there appeared to be a complete absence 
of a mucous envelope. The spines are hollow, greatly attenuated, and their 
apices drawn out into very sharp points. The single pyrenoids in each cell 
were conspicuous. 
