Flagellata and Primitive Algcs. 
107 
RECENT WORK ON FLAGELLATA AND 
PRIMITIVE ALGi®. 
By F. Cavers. 
(Continued from p. 83 f 
O F the unicellular Chlamydomonadaceae, Chlorogonium (Fig. 4, 
F, G, H) is probably on the whole the most primitive. In its 
elongated spindle-like form, this genus differs from the majority of 
the Volvocales, but an approach to the same shape is seen in 
Carteria obUisa , and the zoogametes of Stephanosphcera are spindle- 
shaped. In Chlorogonium the cell divides transversely to form a row 
of four daughter-cells, but these at once become elongated and 
slide past each other, acquiring the spindle form. Transverse 
division occurs in some species of Chlamydomonas (Fig. 4, B), 
though here, as in Sphoerella , division is originally longitudinal and 
there is rotation of the dividing protoplast. In Chlorogonium the 
chloroplast is ill-defined and spongy and varies considerably in 
form, being in some cases ring-like or even spiral, hence sym¬ 
metrical halving can be attained without the longitudinal division 
which is apparently essential in forms with a basin-shaped chloro¬ 
plast ; there are numerous (up to sixty) pyrenoids and about a 
dozen contractile vacuoles (Jacobsen, 61). Cercidium resembles 
Chlorogonium, but has only two pyrenoids and two vacuoles. 
Other simple forms are Chlamydomonas (Fig 4, A to D) and 
Chloromonas, the former with pyrenoids (typically one, but some¬ 
times more) and the latter with none. Pascher’s new genus Agloe 
(Fig. 4, E) is allied to these forms, but its chloroplast is peculiar 
in structure, resembling two conical flasks placed base to base and 
being H-shaped in optical section, with a pyrenoid in the middle of 
the transverse plate-like portion, and there are numerous contractile 
vacuoles. Glceomonas is an imperfectly known genus, probably allied 
to Chloromonas but with several chloroplasts. Various other genera 
have been described which probably represent offshoots from the 
Chlamydomonas type, though some of them are imperfectly known. 
Thus, Coccomonas (Fig. 4, J, K) appears to differ from Chlamydomonas 
chiefly in having a greatly thickened wall, often four-angled; 
Pteromonas (Fig. 4, L, M) is also thick-walled, the wall projecting 
as two lateral wings, as in the Carteriaceous genus Scherffelia; 
while Phacotus has a sculptured wall consisting of two loosely 
connected valves which separate to let the daughter-cells escape. 
Another elaboration is seen in Brachiomonas (Fig. 4, P, Q) and 
Lobomonas (Fig. 4, M, N); in the former the cell has a pointed 
posterior process and from its rounded anterior end there spring 
four recurved processes, in the latter the ovoid cell is produced into 
several rounded wart-like out-growths. In Brachiomonas (Fig. 4, 
R, S) the daughter-cells acquire the form of the parent before 
escaping (Teodoresco, 14 0; West, 147); as pointed out by 
