130 SEAWEEDS 
through the bursting of the apex. They gain access 
to the oosphere by its apical opening and impregnate 
it. The oospore thus formed invests itself with a 
wall, assumes a brownish colour, and generally under- 
goes a period of rest before germination. The plants 
that result from this germination are commonly 
reproduced by non-sexual means for several genera- 
tions of individuals before antheridia and oogonia 
are formed again. 
Zoosporangia, usually slightly club-shaped, are 
produced by the formation of a cross-wall near the 
end of a filament. The contents of the cell so formed, 
which are rich in green colouring matter, gradually 
contract into an oval shape, and escape by the 
bursting of the wall at the apex. There is thus 
normally but one zoospore in each zoosporangium, 
and it is large and ciliated at all points, except in 
some cases the posterior portion. These cilia are in 
pairs, and immediately beneath each pair there is a 
nucleus near the surface, as if the whole body 
represented an aggregate of zoospores which have 
failed to separate. In the formation of zoospores in 
other Chlorophycee, there is usually one formed for 
each nucleus in the parent cell, and it is only natural 
to regard the case of Vaucheria in the light indicated, 
as pointed out by Schmitz, who first observed it. It 
is more than a mere case of preserving -the multi- 
nucleate character of the parent cell, since there is 
this definite relation of nuclei to pairs of cilia. It 
is of interest in this connection to note that during 
the escape of this great zoospore it sometimes gets 
nipped in two by the wall in passing the opening, and 
