124 



THE RISE OF ANIMAL LIFE 



Codosiga 



Hemotococcus Peramma 



Fig. 7-16. Various types of fresh-water flagellates. 



Cbilomonas 



(Fig. 7-16), live in stagnant water where 

 they feed upon bacteria or other smaller 

 Protozoa. Although in its normal environ- 

 ment Chilomonas seems to live on a com- 

 plex diet, it can be grown in a test tube on 

 a diet consisting of ammonia, as a source 

 of nitrogen, and carbon dioxide, as a car- 

 bon source. Here apparently is an organism 

 that in nature lives much like an animal but 

 in the laboratory can be forced to live like 

 a plant, or even more simply, since it does 

 not require nitrogen in the form of nitrates. 

 This may mean that Chilomonas has a full 

 set of enzymes to utilize very simple food 

 sources for the construction of its proto- 

 plasm, but since it is not forced to use them 

 normally, has taken up the animal type of 

 nutrition. This would mean that this small 

 organism had a very simple beginning and 

 has not changed much through millions of 

 years of evolution. 



Most colorless flagellates live as single 



Fig. 7-17. This is a colonial colorless flagellate, Synura 

 uvella, which conveys bad odors to water supplies 

 by the release of aromatic oils when its body de- 

 composes. This is a plastic model. 



