212 CYSTIPHORS. 
Microcystis protogenita. (Bias.) Rabh. dig. Eur. 11, 51. 
Thallus membranaceous, thin, green; families small, angular 
from mutual pressure; cells small, spherical; cell-contents 
granular, pale blue-green. 
Size. Families,-02 mm. Cells, 0015-002 mm. 
Micraloa protogenita, Bias. Alg. Micr. t. xix. Meneg. Nost. 
t. xiv., fig. 1 (partly). 
In water long standing, stagnant ditches, amongst other 
Algae, &c. 
Plate LXXXVI. fig. 5. Families magnified 400 diam. 
Microcystis marginata. (JJeneg.) Kirch. Alg. Schl. 255, 
Thallus spherical, flattened, or orbicular and lens-shaped, 
sometimes confluent, pale-green, colourless at the margin; cells 
minute; cell contents blue-green, at length granular. 
Size. Cells 003-004 mm. Families ‘8--03 mm. 
Anacystis marginata, Meneg. Nost. 98, t,13,f.1, Rabh. Alg. 
Eur. ii., 52. 
In ditches, free swimming. 
Plate LXXXVI, fig.6. Families magnified 400 diam. 
Genus 85. CLATHROCYSTIS. Henfrey. (1856.) 
Frond, a microscopic gelatinous body, at first solid, then 
saccate, ultimately clathrate (fragments of the broken fronds 
occurring in irregularly lobed forms) composed of a colourless 
matrix, in which are imbedded innumerable minute cells, which 
multiply by division within the frond as it increases in size.— 
Quart. Journ. Micr. Sci., 1856, p. 53. 
Clathrocystis sae aa ‘ Henf. Micr. Journ. 1856, p. 53, t. 4, , 
. 28-36. 
Fronds floating in vast strata on freshwater pools, forming a 
bright green scum, presenting to the naked eye a finely granular 
appearance ; when dried, appearing like a crust of verdigris ; 
cells minute. 
Size. Fronds :03-13 mm.; cells ‘0025-0035 mm. 
Rabh. Alg. Eur. ii., 54. Kirch. Alg. Schles. 254. 
Microcystis eruginosa, Kutz. Tab.i., t. 8. 
Polycystis eruginosa, Kutz. Spec. 210. 
On fresh water lakes. 
“The smallest fronds met with are usually roundish or ellipsoidal. 
When quite young they appear to be solid, but as they grow by the multi- 
plication of the internal cells and the secretion of gelatinous matter, the 
expansion takes place chiefly near the periphery, so that the frond becomes 
a hollow body. The walls of the sac then give way, and, as the expan- 
