20 MF/riTOD^ or TWEf^TTaArrox 



experiments, thus showing that if any oxygen remained, 

 its tension must have been small indeed. 



Barron (1932) devised a method for exposing the re- 

 productive cells of marine invertebrates to anoxic condi- 

 tions; (the method could also be used with larger organ- 

 isms). He connected with glass tubing three specimen- 

 bottles of 150 cc. capacity, tightly closed with rubber 

 stoppers. The first bottle contained water and was con- 

 nected with the nitrogen tank. The second bottle con- 

 tained the eggs in 50 cc. sea water and the last bottle 

 contained a solution of safranin T in Sorensen's phos- 

 phate buffer of pH 8.0 and some platinum asbestos. 

 The safranin was first reduced to its leuco form by hy- 

 drogen (with platinized asbestos). After this had been 

 done, the nitrogen, purified according to the method of 

 Michaelis and Flexner (1928), was bubbled through the 

 system for the whole duration of the experiment. As 

 long as the safranin remains absolutely colorless, anaer- 

 obic conditions persist in the system. Barron (1932) 

 points out that safranin has advantages (because of its 

 low oxidation-reduction potential) over methylene blue 

 or indophenol, reagents that are frequently used in their 

 reduced form to indicate the absence of oxygen. 



Concluding remarks. The method to be selected for 

 a particular experiment will depend on the aim of that 

 experiment as well as on the type of material used. 



It seems to the present writer that sometimes miscon- 

 ceptions exist as to the term ''life without oxygen" 

 which unfairly influence the verdict on a particular work. 

 Many investigations have as their primary purpose the 

 study of the metabolic processes that take place when 

 oxygen is excluded. In these cases — especially with or- 

 ganisms whose oxygen consumption begins to decline 

 already at relatively high oxygen tensions — no serious 

 error results if small traces of oxygen remain in the 

 medium. In other cases, e.g., in work with very small 

 organisms that usually can obtain relatively significant 



