THALLOPHYTA 319 
CHLAMYDOMONAS 
Cell structure. The genus Chlamydomonas is an interesting uni- 
cellular form which is clearly intermediate between the flagellates 
and many of the higher 
green alge. The cells 
of Chlamydomonas are 
spherical, oval, or some- 
what cylindrical. They 
are surrounded by cell 
walls, and each indi- 
vidual has two cilia or 
flagella at its anterior 
end (Fig. 320). The 
term celium is more 
inclusive than flagel- 
lum, a flagellum being 
Fig. 821. Palmella state of Chlamydomonas a long, mobile cilium. 
Redrawn after Goroschankin from Oltmanns The protoplasm at the 
anterior end is clear 
and contains two pulsating vacuoles. Most species of Chlamydo- 
monas have a red spot, called the eyespot, which is usually at 
the anterior end. The cell con- 
tains a chloroplastid which, typi- 
cally, is cup-shaped and contains 
a pyrenoid. Pyrenoids are found 
in the chloroplastids of many 
green alow and usually consist 
of a central protein portion sur- 
rounded by starch. In many 
cases the pyrenoids seem to be 
connected with the formation of 
starch. 
Chlamydomonas has what is 
known as a palmella stage, dur-  Fyq. 322. Division of Chlamydo- 
ing which it loses its cilia and monas angulosa into daughter cells 
may divide to form numerous Redrawn after Dill 


