330 
plant and animal kingdoms. 
THALLOPHYTES 
The protoplast is naked or in- 
vested by a membrane which usually contains no cellulose. 
They are commonly abundant in stagnant water and among 
Green Algae some are usually present. 
Euglena represented in Figure 284 is one of the most common 
of the 300 or more species and will serve to show the structure 
and habits of the group. Euglena is quite commonly seen 
Fic. 284. A common species of 
Euglena (Euglena gracilis). At the 
left, an adult individual, showing the 
flagellum, the pulsating vacuole (p), 
the chloroplast (c), and the nucleus 
(n) (X 650); at the right and below, 
Euglena in the spore stage (X 1000); 
at the right and above, a spore germi- 
nating and producing four new indi- 
viduals (X 1000). Redrawn from 
Zumstein. 
swimming about under the 
microscope when Algae are be- 
ing examined. The slender 
unicellular body bears a long 
terminal flagellum, has a chlo- 
roplast, eye-spot, and pulsating 
vacuole. These structures are 
characteristic of the Algae, 
such as Volvocales and also of 
protozoa, the one-celled ani- 
mals. No sexuality is known, 
and multiplication is effected 
by longitudinal fission, a 
method characteristic of the 
lower animals. At the ap- 
proach of unfavorable condi- 
tions, as in autumn, it trans- 
forms itself into a thick-walled 
resting spore which germinates 
and produces one or more new 
plants when favorable condi- 
tions return. Although it 
usually makes its own food, 
sometimes Euglena loses its 
chlorophyll and lives on organic solutions as a saprophyte, thus 
demonstrating that the saprophytic may readily originate from 
the independent habit. 
Many of the Flagellates change their forms readily like the 
Amoeba. 
Sometimes the individuals form colonies of various 
shapes and often variously branched. 
Such features as the possession of chlorophyll and the forma- 
tion of thick-walled resting spores suggest a relationship of the 
Flagellates to plants, while their swimming habits, amoeboid 
