ALG 57 
The exact affinities of many of the Siphonew are still 
obscure, and it is by no means impossible that the group 
has had a multiple origin, ¢.e. all the members of the 
order may not neces- 
sarily be genetically 
related, but there may 
have been a develop- 
ment of this peculiar 
type from several an- 
cestral forms. While 
the lowest of the or- 
der show much in 
common with the 
Protococcacer, and 
may, perhaps, have 
arisen from them, 
others like the com- 
mon genus Vaucheria 
(Fig. 12) are struct- 
urally more like 
some of the Confer- 
vacee. There are a 
number of genera 
among the latter 
where the elongated 
cells are multinucle- 
ate and there is a 
partial suppression 
of the division walls, 
Fic. 12.—Vaucheria sessilis, one of the 
fresh-water Siphonex; A, plant with 
unopened antheridium, an, and o6go- 
nium, og; B, an older plant with the 
autheridium empty, and the odgonium 
containing the resting-spore, sp; C, the 
end of a filament with a zodsporangium ; 
D, zoéspore showing the pairs of cilia 
corresponding to the individual nuclei 
in its outer part; E, a germinating 
zoospore. 
nuclear division and cell division being quite indepen- 
dent of each other. 
By: the complete suppression of the 
division walls in forms like these, it is conceivable that 
