280 МВ. G. 8. WEST ON SOME CRITICAL GREEN АТОМ. 
The discovery of this Alga adds a second species to a genus which has хо 
far been known only by the solitary species Polychetophora lamellosa, W.& 
G. S. West '. 
The specimens were collected in 1901 on the shores of Lough Gartan, 
Donegal, and occurred as epiphytes on various aquatic flowering plants. 
The cells are globose or ovoid in form, rather small, and destitute of any 
appreciable mucous envelope. They are solitary, or occur two or three 
together, having but a slight attachment to the plant upon which they grow. 
There is a distinct dorsiventrality about the cells, although there is no attempt 
at the formation of either a creeping filament or a flat plate. The ventral 
part of the cell is attached to the substratum, and the other part, which may 
he regarded as dorsal, is furnished with from two to four simple, but greatly 
elongated bristles. There is one parietal chloroplast in each cell, normally 
somewhat cup-shaped and occupying the ventral wall. No pyrenoids were 
observed, but several scattered granules of minute size, which stained blue- 
black with chlor-zine-iodine, were observed in some of the cells. These were 
most probably small granules of starch (fig. 6). A small nucleus is present 
towards one side of the hollow in the cup-shaped chloroplast (fig. 6, 4). 
Polychætophora simpler differs from P. lamellosa in the smaller size of its 
cells, in the very much thinner cell-wall, which is not lamellose, and in the 
restricted number of bristles. From eight to twelve of the latter are present 
in P. lamellosa, and they are distributed all round the exterior of the cell, 
whereas there are only two to four bristles in P. simpler, and their dorsal 
attachment is a conspicuous feature of the species. 
The genus Polychetophora belongs to the Cheetopeltides, а small family 
distinguished from the rest of the Protococcoideæ hy the presence of setze or 
bristles. 
Nothing is known of the reproduction of Polychetophora, but т P. lamel- 
losa multiplication takes place by the division of the cells in one plane and 
the formation of a short irregular chain. This short filament, consisting of 
about eight cells, subsequently breaks up, cach cell being able under suitable 
conditions to form a new chain. 
It is possible that Polychetophora simplex, or a closely allied Alga, is 
responsible for the confusion which has existed concerning the identity of 
Glæochete Wittrockiana. The latter was described by Lagerheim? from Sweden 
as a blue-green Alga, and I have since found it repeatedly. There is not the 
slightest question that it is one of the Myxophyceæ ? of the subfamily Chroo- 
cystee, with a cytological structure closely akin to that of Chrooeoccus, Yet 
1 W. & G. S. West, “ Notes on Freshwater Algie.—IIL," Journ. Bot. xli, (1903) p. 79, t. 448. 
? G. Lagerheim, “ Bidrag till Sver. Algafl.,” Otvers. К. Sv. Vet.-Akad. Fórh. (1883), по. 2, 
p. 39, t. 1. f. 3-4; Nuova Notarisia (1890), p. 251. 
з G. S, West, © Alga-fl. Cambs..” in Journ, Bot, xxxvii, (1899) р. 264, 
