So F. Cavers. 
V.-VOLVOCALES. 
The Polyblepharidaceae are included in the Volvocales by 
Blackman and Tansley (7), Wille (150), and various other writers, 
though Fritsch (46) regards them as still belonging to the Flagellata, 
but it appears quite immaterial how this family is placed in a formal 
scheme of classification, so long as it is recognised that no sharp 
line of division separates the Flagellata from the lower Algae and 
that this remarkable transitional family shows an extraordinarily 
even balance between the two groups. The Polyblepharids agree 
with typical Flagellates in being devoid of a definite cellulose wall 
and in undergoing longitudinal division in the motile phase—but it 
should be noted that in several genera of Volvocales ( Chlorogonium , 
Brachiomouas, and even colonial genera like Gonium and the 
oogamous Eudorina) division may occur while the flagella are still 
motile. The Polyblepharids have the characteristic basin-shaped 
Volvocine chromatophore and a pyrenoid, but—as will appear 
later—the Cryptomonads and some of the other Chrysomonadineae 
would have as much right to a position among the Algae as have 
the Polyblepharids if the possession of Algal chromatophores, 
pyrenoids, starch, and a firm periplast allowing of only slight 
changes of shape be taken as definitely Algal characters; while, on 
the other hand, the fact that sexual reproduction occurs in a Poly- 
blepharid (Dunaliella) cannot now be regarded as an argument 
against the reference of this family to Flagellata rather than to 
Algae. 
Probably the most primitive genus of Polyblepharidaceae is 
Polyblepharis (Fig. 2, A), in which the broader anterior end of the 
conical body bears from six to eight flagella in a tuft; in Pyramimonas 
(Griffiths, 52; Fig. 2, B, C) there are four flagella arising from a 
depression at this end, which is four-lobed, as is also the chromato¬ 
phore; in Chloraster ( Fig. 2, D) there is a central fifth flagellum; 
while in Tetratoma, a somewhat doubtful and incompletely known 
form, there are four flagella inserted at separate points on the 
anterior half of the spherical body. The genus Dunaliella (Fig. 2, 
E to L), recently described by Hamburger (53) and by Teodoresco 
(140, 141), evidently forms a transition from the Polyblepharidaceae 
to the Chlamydomonads, since it has only two flagella and shows 
conjugation of isogamous zoogametes; while Stephanoptera, recently 
discovered by Dangeard (35), resembles Pyramimonas in structure 
but has only two flagella, thus connecting Pyramimonas with Duna¬ 
liella —according to Dangeard, the life-cycle of Stephanoptera ends 
in encystment, the cyst having sometimes two nuclei instead of one, 
but the fate of the cyst was not determined. To the Polyble- 
pharidacese probably also belongs the genus Chlorodendron (Fig. 2, 
M to B), placed by Oltmanns (95) in a special family (Chloroden- 
draceae), with the closely related, or perhaps congeneric, forms 
Prasinocladus lubricus Kuckuck and Euglenopsis subsalsa Davis— 
these have recently been investigated by Dangeard (34, 36) who 
regards these forms as being closely related to the Carteriaceae 
(see below). In the Chlorodendreae, branching colonies are produced 
by the localised secretion of mucilage derived from the periplast, or 
cell-wall, of the dividing cells, and this family, or sub-family, forms 
