ALG 
53° 
are always biciliate, and are set free in the water where 
they unite in pairs to form a single cell (zygote) with 
four cilia (Fig. 8, D), which either at once grows into 
a new plant, or first 
passes into a resting 
stage (spore), which 
then gives rise to new 
individuals by first form- 
ing one or more z006- 
spores. 
In the higher mem- 
bers of the order, the so- 
called odgamous forms, 
there is a sharp separa- 
tion of the sexual cells, 
the female cell becoming 
here a large passive cell, 
the egg-cell, usually 
borne in a specially 
modified and enlarged 
cell called the o6gonium 
(Fig. 9, 0g). In the 
form figured, the egg 
closely resembles in its 
formation and structure 
the large zodspores, with 
which it agrees except 
in the absence of cilia, 
Fic. 9. (Confervacee).— A, B, por- 
tions of two female plants of Gtdo- 
gonium ; og, the odgonium; in A, the 
egg-cell has not yet' been fertilized, 
in B, the fertilized egg has become 
transformed into a thick-walled rest- 
ing-spore ; the spermatozoid enters 
through the pore at the top; C, part 
of a male plant of the same species, 
showing the antheridium, an; D,a 
zoospore or motile non-sexual repro- 
ductive cell; E, one-celled plant de- 
rived from a zoospore ; F, the lower 
part of an older plant showing the 
gatas outgrowths (7) of the basal 
cell. 
and there is no question that here also the gametes are 
modifications of originally non-sexual zodspores. The 
male gametes (spermatozoids) in these odgamous Con- 
fervacez are also borne in special cells (antheridia) (Hig. 
