82 
F. Cavers. 
contractile vacuoles are found not only in Sphcerella but also in 
CJilorogonium (which differs from the Polyblepharids and most of 
the simpler Chlamydomonads in showing transverse instead of 
longitudinal division), and in Agloe, a form with somewhat specialized 
cell structure. Cartcrin and Spondylotnorum agree in having four 
flagella and in other characters, but though Carteria is usually 
stated to have a pyrenoid, Jacobsen (61) has described a species 
(C. ovata) which has none ; according to this writer, Spondylotnorum 
is also without a pyrenoid ; while Chloromonas is distinguished from 
its ally Chlamydomonas solely on the ground that it lacks a pyrenoid, 
but this simply means that systematists have described pyrenoidless 
species or even varieties (Serbinow, 137) of Chlamydomonas as 
belonging to a distinct genus—on other grounds, there is little 
doubt that Clilamydotnonas and Chloromonas are quite unnatural 
genera, and will probably have to be revised and split up as the 
result of further investigations. Most of the Volvocales have a 
single pyrenoid, but in Chlamydomonas inhcerens (Bachmann, 3) 
two or three of these bodies may be present, while in C. coccifera 
(Goroschankin, 51, iii) there are five to eight pyrenoids ; two occur 
in Sphcerella Drcebakeusis and in Stephanosplicera, while Sphcerella 
pluvialis, Chlorogonium, and Pleodorina have a large number of 
pyrenoids. 
Fig. 3. CARTERIACEjE.—A, Carteria ovata Jacobsen : this species has 
no pyrenoid , the chromatophore contains numerous small starch grains. 
B, C, Scherffelia phacus Pascher: C shows the cell cut across, to make clearer 
the wing-like expansion of the cell-wall and the structure of the U-shaped 
chromatophore. D to G, Spondylotnorum quaternarium Ehrb.: D, a normal 
sixteen-celled coenobium ; E, an eight celled coenobium; F, division of each 
cell to form a daughter coenobium ; G, daughter coenobium not yet set free 
from mother-cell. A, D to G, from Jacobsen ; B, C, from Pascher. 
The family Carteriacese includes Carteria (Fig. 3, A), which has 
a very thin wall; Scherffelia (Fig. 3, B, C), in which the cell is 
flattened, oval in outline and slightly biconvex in cross-section, 
