Flagellata and Primitive Alga. 109 
in M the liberation of the four daughter-cells. N, O, Lobomouas Francei Dang. 
P to S. Bvachiomonas submarina Bohlin : P and R in side view, Q and S in 
anterior view ; in R and S the formation of daughter cells. T to V, Platydorina 
caudata Kofoid : T, surface view ; U, side view, showing the slight spiral twisting 
of the plate-like coenobium ; V, a single cell. W, Stephanoon Ashenasii Schewk. 
X, Pleodorina illinoisensis Kofoid (the four small vegetative cells are shown at 
the left). 
A to D, F to H, from Jacobsen ; E, from Pascher ; J, K, from Stein; L, 
M, from VVille ; N, O. from Dangeard : P, Q, R, S, from West; T, U, V, X, 
from Kofoid; VV, from Schewiakoff. 
Fritsch (46) this recalls the autospore formation characteristic 
of the Scenedesmaceae and Phytheliaceae among the Protococcales. 
Included in the unicellular Chlamydomonadaceae are two colourless 
saprophytic forms— Polytoma (France, 43; Prowazek, 117) which 
is probably derived from Chlamydomonas, and Chlamydoblepharis 
which resembles Coccomonas. In his recent classification of the 
Volvocales, Wille (150) includes in the Chlamydomonadaceae the 
genera Nephroselmis and Glocococcus , but the former is better placed 
among the Cryptomonads, while the latter belongs to Tetrasporaceae. 
Of the six genera appended by Wille to the Volvocales as doubtful 
forms, Gleeomonas may be placed near Chloromonas, despite its 
possession of numerous chloroplasts; Cylindromonas and Mesostiguia 
probably belong to Euglenineae, and Tetratoma to Carteriaceae; 
Xanthodiscus and Kleiniella are still imperfectly known, though 
Lemmermann (85) places the former in the Cryptomonadineae, 
while France (43) regards Kleiniella as allied to Coccomonas and 
Chlamydoblepharis. 
As pointed out by Fritsch (46), of the three attempts at coeno¬ 
bium formation seen in the Volvocales, that represented by Gonium 
has alone proved successful and has given rise to the remarkably 
complete ascending series which culminates in Volvox. Schussnig 
(133) has recently described in detail the life history of Gonium 
pectorale , and has shown that in addition to the formation of daughter 
colonies and zoogonidia, reproduction occurs by means of aplano- 
spores and by the conjugation of isogamous zoogametes; while 
Harper (54) has carefully studied the structure and division of the 
Gonium colony. Pringsheim’s observation that Pandorina shows 
heterogamy does not appear to have been repeated by recent writers 
on the life history of this genus ; while no further observations on 
the peculiar genus Platydorina (Fig. 4, T to V) have apparently been 
made since its discovery by Kofoid (70) and its life history is still 
unknown. Schewiakoff’s genera Mastigosphcera and Stephanoon (126) 
appear to bridge the gap between Pandorina and Eudorina, though 
their life history is unknown. In Mastigosphcera, the cells, which 
have but one flagellum, are less closely packed in the spherical 
coenobium than is the case in Pandorina; while in Stephanoon 
(Fig. 4, W) the cells are arranged on the equator of the coenobium, 
as in Stephanosphcera, but in two alternating rows. In Eudorina the 
cells are spaced out at the periphery of the spherical coenobium, 
though showing a tendency to be arranged in circles, but all the 
cells are alike capable of reproduction, whereas in Pleodorina and 
Volvox there is differentiation into vegetative and reproductive cells. 
Until recently, Pleodorina with two species— P. californica Shaw 
(138), P. illinoisensis Kofoid (69)—was known only from the United 
