134 BOTANY. 
the female organ consists of a rounded germ-cell situated 
within a cavity—the odgone; it is developed from one of 
the cells (sometimes two) of the filament by a condensing 
and rounding off of the protoplasmic contents; when the 
germ-cell is fully mature, an opening is formed in the 
odgone-wall for the ingress of the antherozoids (A and B, 
Fig. 62). One or more antherozoids are produced in cer- 
tain small cells of the same or another filament; in shape 
they resemble the zodspores mentioned above. Upon es- 
caping into the water they swim about vigorously, eventu- 
ally making their way through the opening in the odgone, 
and then burying themselves in the substance of the germ- 
cell (B, 2, Fig. 62). After fertilization, the germ-cell be- 
comes covered with a thick and colored (brown or red) 
coat, and it then becomes a resting spore. 
279. After a period of rest, the resting spore germinates 
by rupturing its thick coat and permitting the escape of 
the contents, enclosed in a thin envelope; by this time the 
protoplasm has divided into four portions, which take on 
an oval form and develop a crown of cilia. They soon 
escape from the investing membrane, and after a brief 
period of activity grow into an ordinary filament in exactly 
the same manner as the zodspores. 
Practical Studies.—(a) In midsummer collect a few quarts of the 
surface-water of weedy ponds, together with the Pond Scums grow- 
ing therein; put it into a shallow dish, and after an hour or so look 
carefully (with the naked eye)for Volvox. It will beseen as a minute 
green ball (from .5 to 1 millimetre in diameter) rolling slowly through 
the water. Now carefully transfer it to a slide along with enough 
Pond Scum to prevent crushing. Under even a low power many of 
the details of structure may be made out, and one or more young 
colonies in the interior may almost invariably be seen. 
(5) Specimens of @idogonium may be obtained by examining the 
small sticks and stems of aquatic plants from quiet waters, They 
may be recognized by the enlarged cells (odgones). 
