Algae and the Principles of their Evolution. 107 
zoid and oosphere of Volvox , there are the two graduated 
intermediate stages in Pandorina and Eudorina . 
Protoeoccaceae. — In the same way that it is possible 
to derive the Volvocineae theoretically from the Palmellaceae 
by the prevalence of one of their peculiarities, namely, their 
motile stage, it is not less natural to imagine a similar origin 
for the Protococcoideae, in which group the motionless 
sporangium-stage is the most important. 
As the close connexion between the two groups is not so 
clearly apparent as in the former case, we may consider the 
Protococcoideae either as the product of a special evolution 
from a reduced stage of filamentous Algae ; or else, as appears 
to me more natural, as the direct product of the evolution 
of sporangium-conditions in supposed Palmellaceae. 
In the lower forms there are globular cells with smooth 
or more or less ornamented cell-walls ; the latter are generally 
the firmest. Their propagation takes place by the develop- 
ment of zoospores or spores. All their reproductive processes, 
however, show a very marked tendency to transform these 
motile elements into resting-spores. 
We have in Golenkinia radiata (Chod.) 1 2 a particularly 
instructive case. The globular cell has a rather thick cell- 
wall with filiform radiating prolongations ; multiplication 
takes place by discharging four naked and half-amoeboid 
spores, which soon become clothed ; in other cases the cell 
can be revived by the extrusion of its cell-contents provided 
with a new smooth though thin cell-wall. Multiplication 
in this stage takes place by the production of quadriciliate 
zoospores. I have also described the same in the case of a 
gelatinous Gloeocystis-c ondition. The production of motile 
elements is replaced in the adult stage by naked non-motile 
spores, which under special conditions may be transformed 
into very definite spores with thick cell-walls. 
P almellococcus 2 is a genus producing in its natural habitat 
1 Chodat, Golenkinia radiata , Journ. de Botanique, 1894, tab. 8, p. 305. 
2 Chodat, Materiaux, I, p. 600, loc. cit. 
