PROTOCOOCACE. 39 
Ophiocytium, “ Science Gossip,” June, 1867, p. 127, fig. 103. 
In pools, mixed with other alge. 
ga AIV. fig. 2. a, young cells; ¢, older cells; b, mature cell X 
Genus 28. SCIADIUM. Braun. (1855.) 
Plant from a single individual producing a family. Thallus 
(solitary) adnate, unicellular ; cell elongated, cylindrical, 
straight, attenuated at the base into a slender stem. Gonidia 
about 8, resulting from division of the cell-contents, ai length 
protruding from the ruptured apex, retained at the mouth and 
extending in the form of an umbel, each individual becoming 
developed into a cylindrical cell like the mother-cell. This pro- 
cess is repeated to a third, or sometimes a fourth generation, 
forming a composite or decomposite umbel. Ultimate cells 
producing free biciliate zoogonidia. 
The cylindrical cell of Sciadiwm possesses uniformly distributed green 
contents, which are interrupted, in perfectly developed cells, by light 
cross streaks, and are divided into a row of 5 to 8 about equal masses, 
which become gonidia. I could not detect nuclei in the individual seg- 
ments of the contents- passing into the formation of gonidia.—Braun 
Rejuvenescence, p. 260. 
Sciadium arbuscula. Brawn Unicell. Alg. p. 106, t. 4. 
Umbellate. Cells straight (rarely falcate), obtuse at the apex ; 
stem about as long as the diameter of the cells. 
Size. Cells 0038 mm. (rarely ‘(007 mm.) diam. 
Sciadium arbuscula, Micr. Journ., 1866, p. 4. Archer, Micr. 
Journ. xii., 1872, p. 314. 
Ophiocytium arbuscula (Br.), Rabh. Alg. Eur. iii, 68, 
Attached to confervoid alge and aquatic plants, 
Braun, writing of this species, says—“ It displays an originally obovate 
tube, generally becoming elongated into a cylindrical form, obtuse 
above, and prolonged into a slender attached pedicel below. The con- 
tents consist of uniformly green mucilage, in which a small vesicle 
may sometimes be distinguished, but only in the earliest stage of growth. 
The pedicel is transparent and colourless, and secretes at its base an 
originally yellowish brown, afterwards dark brown mass, which gradually 
expands into a disc-shaped foot. When the growth is completed the 
green contents become divided into several masses, developing into a 
series of 5-8 germ cells; the cell membrane dehisces, throwing off its 
summit as a finger-stall-shaped cover, but the germ cells, instead of 
leaving the open tube, all collect at the point of exit with their inferior, 
narrower, and somewhat pedicellately elongated ends sticking in the 
tube. Thus is produced a capitule, and by the advancing growth of the 
young family an umbel formed of individuals exactly resembling the 
parent individual from which they originated. The emptied mother-cell 
tube remains as the stem and support of the umbellate family, and 
gradually becomes filled from above downwards with the same yellow and 
reddish brown secreted substance which it exhibits at its own base. The 
