434 Physiology 



organic materials. Whether autotrophic nutrition should be considered 

 primitive or not, the food requirements of the supposedly autotrophic 

 phytoflagellates differ considerably from those of other Protozoa. 



Chemoautotrophic, photoautotrophic, and heteroautotrophic nutrition 

 have been reported in various phytoflagellates (Table 8. 2). Three species 

 have been giown under conditions suggesting chemoautotrophy — two of 

 the three in glass-covered culture vessels. The investigation of chemo- 

 autotrophic nutrition illustrates, to an extreme degree, the difficulties in- 

 herent in the use of media supplying a bare minimum for growth. After 

 an adequate number of transfers, it may be concluded that the food sup- 

 ply of the organism is limited to constituents of the test medium — plus 

 any contaminants absorbed from glassware, introduced by way of dis- 

 tilled water, stock solutions and dust or absorbed from the air. The first 

 obvious refinement in technique is the elimination of cotton plugs from 

 culture tubes or flasks. Although bleached cotton may be inactive as a 

 source of thiamine or its components (509), plugs of this material con- 

 tribute significantly to the growth of Chilojnonas Paramecium in an in- 

 organic medium and the effect is not eliminated by the addition of 

 thiamine in excess (73). Organic pollution of distilled water and stock 

 solutions by bacterial growth can be avoided by aseptic techniques or by 

 the use of a volatile preservative (227). However, other difficulties remain. 

 Certain inorganic salts used for culture media contain organic contami- 

 nants, which in terms of carbon balance could account for the observed 

 growth in an experimental medium (73). Furthermore, there must be a 

 demonstrable inorganic soiuce of energy. In the case of Chilomonas para- 

 7necium, there is no significant oxidation of ammonia (73), although 

 tests have not been reported for several other "chemoautotrophs." Ac- 

 cordingly, it must be concluded that the evidence for chemoautotrophy 

 in Protozoa is still inadequate, and that under experimental conditions 

 now attainable it is seemingly impossible to limit a flagellate to chemo- 

 autotrophic nutrition. 



So far as photoautotrophic nutrition is concerned, it should be much 

 less difficult to prove that organic contaminants are an unimportant factor 

 in growth. In this connection, the failure of Chlamydomonas moexvusii 

 to grow without both light and carbon dioxide — even in inorganic media 

 supplemented with a variety of nitrogen sources, vitamins and oxidizable 

 carbon sources — seems very significant (315). Investigations are still 

 handicapped, however, by inadequate knowledge of qualitative and quan- 

 titative mineral requirements. "Photoautotrophic" nutrition has been re- 

 ported in several Phytomonadida and Euglenida (Table 8. 2). In most 

 cases, culture vessels have been plugged with cotton, but Eudorina elegans 

 (108) has been maintained in all-glass vessels. Such results (109) also have 

 supported earlier observations on Euglena anahaena. Similar confirma- 

 tion is needed for other reports of photoautotrophy. All-glass vessels do 



