VARIATION IN THE DESMIDIER. 387 
In another almost pure gathering of this species from Hanka 
Deela, Somaliland, the specimens were smaller (long. 19:5-28 p ; 
lat. 11:5-17 a; lat. isthm. 3-5 p), more elongate and somewhat 
angular, many of them approaching the var. septentrionale, 
Wille (“ Ferskv. Alg. fra Nov. Seml.,” Ofvers. af K. Vet.-Akad. 
Förh. 1879, no. 5, p. 43, t. 12. f. 34). This variety has been 
considered by some authors to be more nearly related to Cos- 
marium Meneghinii, Bréb. (in Ralfs, Brit. Desm. p. 96, t. xv. 
f. 6) than to C. leve, Rabenh. ; but I think the range of variation 
exhibited by the specimens from Somaliland proves this supposi- 
tion to be erroneous, all intermediate stages between typical 
C. leve and the var. septentrionale being met with in this one 
gathering. 
C. leve var. septentrionale is very frequent in this country, 
and is itself subjeet to a certain amount of variation, especially 
with regard to the angularity of the semicells and the character 
of the superior lateral margins, the latter often exhibiting a 
marked undulation. I figure several such specimens: one from 
Bowness, Westmoreland, long. 25:5 u, lat. 16 p, lat. isthm. 4°8 u, 
crass. 9 u (Pl. 10. fig. 8); one from near Giggleswick, W. Yorks., 
long. 24 u, lat. 15 a, lat. isthm. 5:2 u (Pl. 10. fig. 7) ; and one 
from Epping Forest, Essex, long. 24 p, lat. 15:5 p, lat. isthm. 
5:5 u (Pl. 10. fig. 9). 
The cell-membrane of the ty pical form is delicately scrobiculate, 
but that of the var. septentrionale is generally smooth. 
9. Cosmarium REGNESII, Reinsch, “ Algenfl. von Frank." 
Abhandl. Naturhistor. Gesellsch. Nürnberg, Bd. iii. 1866, p. 112, 
t. 7. f. S. —This minute species is not unfrequent in many of 
the mountain localities rich in Desmids, and any account of its 
various forms must necessarily be of particular interest. 
In a gathering from Sphagnum and Utricularia minor on 
Puttenham Common, Surrey, an immense number of individuals 
were obtained in active division. The specimens were typical in 
size (long. 6-10 u; lat. 6°2-9°5 u; lat. isthm. 347 u; crass. 5 u) 
and many of them typical in outline; č. e., the semicells were 
transversely oblong, with slightly retuse lateral margins, with the 
inferior and superior angles mueronulate, and with two small 
mucros, one on each side of a retuse middle portion of the apex 
(Pl. 10. figs. 10, 12, 13, 15, 16). Some of the specimens, how- 
ever, had the inferior angles of the semicells slightly emarginate, 
