I 10 
F. Cavers. 
States, but P. californica has since been discovered in Ceylon 
(Fritsch, 46), in France (Chatton, 27), and in Java (Woloszynska, 
145), while P. ilUnoisensis has been found near Heidelberg (Merton, 
92), and the life history of this genus has been worked out in detail 
by Chatton and by iMerton. In P. ilUnoisensis (Fig. 4, X) the 
coenobium consists of 32 (more rarely 16 or 64) cells, arranged 
in five circles, the two polar circles having four cells each and the 
other three circles eight cells each ; the cells of the anterior polar 
quartette are vegetative only, never dividing to form new ccenobia 
and are smaller than the remaining cells. This species thus forms 
a transition from Eudorina to Pleodorina californica, in which 
the coenobium consists of 64 or 128 cells and is sharply 
divided into an anterior hemisphere in which the cells are 
purely vegetative and only one-third to one-half as large as the re¬ 
productive cells of the posterior hemisphere. In Pleodorina the 
cells have two contractile vacuoles and numerous pyrenoids, and 
Scyamina 
Volvox 
Pleodorina californica 
Pleodorina illinoisensis 
y Eudorina 
/ Stephanoon (?) 
^ Mastigosphaera (?) 
Pandorina 
T Platydorina 
Gonium —* 
Cloeomonas 
Pteromonas 
Phacotus 
Coccomonas 
>1 
Chlamydoblepharis 
Lobomonas 
Brachiomonas 
, C h. lamydomonas 
/iAgl 
oe 
Polytoma 
T 
Chlorogonium 
T 
Bunaliella 
/t. 
Stephanosphaera 
Sphaerella 
Chlorodendron 
Pyramimonas 
Chloraster 
Polyblepharis 
Spondylomorum 
,Scherffelia 
Chloromonadineae 
Carteria 
N 
Tetrablepharis 
Chrysomonadineae 
Autotrophic Multicilia — like 
Ancestors 
Table B.—Suggested Phylogeny of the Volvocales. For details, see Text. 
the chloroplast is reticulate; in both species, oogamous sexual 
reproduction occurs as in Eudorina, any of the potentially repro¬ 
ductive cells producing either a mass of antherozoids, an oosphere, 
or a daughter-coenobium. The two species of Pleodorina form 
perfect connecting links between Eudorina and Volvox, in which 
last genus the vast majority of the cells in the large coenobium are 
vegetative and there is still more pronounced differentiation between 
