Flagellata and Primitive Algce. 
83 
with a thick wall which in one species is produced into a marginal 
wing on either side, two ehloroplasts which may or may not be 
united behind to form a U-shaped structure (obviously derived from 
splitting of an originally basin-shaped chromatophore), and no 
pyrenoid ; Telrablepharis, a colourless saprophytic form probably 
derived from Carteria ; and Spondylomorum (Fig. 3, D to G), a colonial 
form constructed on a plan quite different from that seen in the 
ccenobial Chlamydomonadaceae and consisting of sixteen Carteria- 
like cells in four alternating tiers of four cells each, attached to a 
gelatinous rod-like axis. Among the Carteriacese, sexual reproduction 
is only known in one or two species of Carteria which produce 
isogamous zoogametes. It is of interest to note that the symbiotic 
“ Zoochlorella ” found in the Planarian worm Convoluta roscojfensis 
(Keeble and Gamble, 65) is a species of Carteria ; the single species 
of Spondylomorum {S. quaternarium), hitherto known only from 
Europe and Asia, has recently been discovered by Campbell (20) 
in California. 
Apart from the Polyblepharidaceae and Carteriacese, the 
Volvocales have a pair of flagella, though a single flagellum occurs 
in a species of Polytoma (Pascher, 108) and in the genus Mastigo- 
sphcera. The Sphaerellaceae, including the unicellular Sphcerella 
(H cematococcus) and the colonial Steplianosphcera, are distinguished 
from the remaining Volvocales—the Chlamydomonadaceae—mainly 
by the peculiar structure of the cell-wall. Various contributions 
to the knowledge of Sphcerella have recently been made, especially 
by Peebles (HO), Reichenow (113), and Wollenweber (145, 146). 
What has usually been taken for a thin outstanding cell-wall is in 
reality a firm outer layer, while the supposed sap-containing space 
between wall and protoplast is a thick inner gelatinous coat, 
traversed by fine branching pits into which protoplasmic threads 
extend. Reichenow has minutely studied the structure and mitotic 
division of the nucleus and the shifting of the originally longitudinal 
axis of division into an oblique or transverse position. The chloro- 
plast is a spongy and reticulate structure, and in S. pluvialis there 
are numerous pyrenoids at the nodes of the network. Though 
Sphcerella has been so much worked at, Miss Peebles appears to 
have been the first to observe a sexual process in this genus; she 
states that when dry encysted cells of 5. pluvialis are moistened 
and exposed to strong light, the contents of the cyst divide into 
eight to sixty-four gametes which fuse in pairs, as is also the case 
in Steplianosphcera. 
{To be continued). 
[Note. —In the first instalment of this article (January number), certain 
alterations inserted at the last moment resulted in misprints. On p. 28, 
“former” (line 7) should, of course, be “formal”; on p. 32, line 3 from 
bottom, for “ form ” read “ forms ” ; on p. 33, top line, for “ Crystoflagellata ” 
read “ Cystoflagellata,” and in line 5 from top “ hetetrotrophic ” should be 
“ heterotrophic.” On p. 33, line 18 from top, the substitution of a note of 
interrogation (?) for a semicolon (;) may be regarded as a piece of unconscious 
humour—though the reader may, like the author, feel inclined to mark each 
of these “ main lines ” with a query !] 
