116 



Comparative Animal Physiology 



tures. Some other chlorophytes (e.g. Chlamydomonas^ can use nitrates in the 

 dark, and some colorless organisms such as Polytoma ocellatum which are 

 restricted to organic acids (acetate) for carbon can use nitrates, whereas some 

 others (Polytom^a, Chilomonas) can use ammonia for their nitrogen. The 

 requirements of chlorophytes may be more complex in the dark than in the 



TABLE 20. GROWTH OF SEVERAL SPECIES OF EUGLENA 

 IN SINGLE AMINO ACIDS'' 



light; Chlamydomonas uses nitrate in Hght, amino acids in the dark. Euglena 

 gracilis, which is photo-autotrophic, can grow in the dark, provided acetate 

 is supplied, and it then can use peptones, ^" or even ammonia, ^-^ while E. 

 deses is said not to grow in the dark even with peptones and acetate. *'*' There 

 must be some enzymatic connection between the utilization of carbon and 

 that of nitrogen. 



All autotrophic organisms can synthesize each of nineteen generally oc- 



