THE GREAT GROUPS OF ALG^E 243 
plasm organized about it is a cell, whether it has a wall or 
not. Therefore the body of Vaucheria is made up of as 
many cells as there are nuclei, cells whose protoplasmic 
structures have not been kept separate by cell walls. Such 
a body, made up of numerous cells, but with no partitions, 
is called a ccenocyte, or it is said to be cwnocytic. Vaucheria 
represents a great group of Chlorophyceae whose members 
have coenocytic bodies, and on this account they are called 
the Siphon forms. 
Vaucheria produces very large zoospores. The tip of a 
branch becomes separated from the rest of the body by a 
partition and thus acts as a sporangium (Fig. 208, B). In 
this improvised sporangium the whole of the contents or- 
ganize a single large zoospore, which is ciliated all over, 
escapes by squeezing through a perforation in the wall 
(Fig. 208, C'), swims about for a time, and finally 
develops another Vaucheria body (Figs. 208, E\ 
209). It should be said that this large body, 
called a zoospore and acting like one, is really 
a mass of small biciliate zoospores, just as the 
FIG. 209. A young Vaucheria, germinating from a 
spore (sp), and showing the holdfast (w). 
After SACHS. 
apparently one-celled vegetative body is really composed of 
many cells. In this large compound zoospore there are 
many nuclei, and in connection with each nucleus two cilia 
are developed. Each nucleus with its cytoplasm and two 
cilia represents a small biciliate zoospore, such as those of 
Cladophora, 165. 
Antheridia and oogonia are also developed. In a com- 
mon form these two sex organs appear as short special 
branches developed on the side of the large coenocytic body, 
