THALLOPHYTES 
35 
Zoos pore. The asexual reproduc- 
tion is modified in an interesting way 
by the coenocytic habit. At the tip 
of a branch a very large zoospore is 
formed by the protoplast, and is cut 
off from the general body by a wall 
( n g- 95)- It is discharged through 
an opening at the end of the branch 
and moves actively by means of cilia 
that are distributed over its whole 
surface (fig. 96). The zoospore is 
multinucleate, containing the nuclei 
that were in the end of the branch at 
the time of its formation, and in con- 
nection with each nucleus a pair of 
cilia is formed. This large zoospore, 
therefore, may be regarded as a com- 
pound zoospore, corresponding to a 
number of biciliate zoospores. It 
FIGS. 95-97. Vaucheria: showing forma- 
tion (95), escape (96), and germination (97) of 
zoospore. After COULTER. 
FIG. 94. Vaucheria: a small portion 
of the filamentous, branching, coenocytic 
body. 
germinates directly, producing a 
new filament (fig. 97). 
Sexual reproduction. The 
structures connected with sexual 
reproduction are more highly 
developed than any previously 
mentioned, for not only is Vau- 
cheria heterogamous, but it pro- 
duces special sex organs which 
are not transformed vegetative 
cells, but are specifically for 
gamete-production from the be- 
ginning. In one of the species, 
for example (fig. 99), a special 
branch is put out from the side 
of the filament, and a terminal 
cell is cut off by a wall and en- 
larges into a more or less globular 
oogonium, in which a single large 
egg (oosphere) is formed. This 
egg at first is multinucleate, but 
