THALLOPHYTA 317 
Relationship of Flagellata. The flagellates are a very interesting 
group; they are clearly on the border line between animals and 
plants, and there are 
reasons for consider- 
ing them as the group 
from which both ani- 
mals and higher plants 
have been derived. 
While at least those 
forms which contain 
chlorophyll may surely 
be regarded as plants, 
the whole group is 
considered by zoolo- 
gists as belonging to 
the animal kingdom, 
and those forms that 

Fie. 318. Huglena gracilis 
Upper left, green form ; upper right, colorless form 
grown in nutrient solution in the dark ; lower left, 
resting spore ; lower right, contents of resting spore 
divided to form four daughter cells. (Redrawn 
after Zumstein) 
lack chlorophyll are certainly like animals in 
their characteristics. A way in which pro- 
tozoa (one-celled animals) may have been de- 
rived from plants is suggested by those forms 
which contain chlorophyll and at the same 5... 319. Division of 
time ingest solid food particles, and by those  wotile cell of Euglena 
which under certain conditions contain chlo- 
rophyll and obtain food by photosynthesis 
and under other conditions lack chlorophyH and live like animals. 
Some of the characteristics of the flagellates which at first 
sight might seem to suggest that they are animals are the very 

Redrawn after Stein 
