EVOLUTION BY ChloreUa: II 



421 



burst rate is shown in Fig. 1* with the accompanying oxygen con- 

 centration changes. Its dui-ation (3 seconds maximum) is shorter than 

 bursts shown in the previous paper and, following a short interval of 

 oxygen uptake, a secondary burst appears partially obscured, in this 

 case, by the initiation of the sustained rate. This provides quantita- 

 tive improvement over the description of anaerobic O2 bursts pre- 

 viously reported by others where such details are obscured by dif- 

 fusion delay and other causes. Other examples of this time course 



Fig. 2. Influence of O2 concentration on the O2 burst maximum. (A) Commercial 

 "Seaford" grade N2 after passing over hot reduced copper; (B) "Seaford" N2 

 (0.002% O2); (C) commercial mixture 5% CO2 and 95% N2 (0.1% O2); (D) com- 

 mercial water pumped N2 (0.5% O2). 



show complete development of the secondary burst and its following 

 period of oxygen uptake by longer anaerobic treatment and are in- 

 cluded among the subsequent figures (Figs. 2, 4, 7, 8). Variability in 

 the magnitude of these effects in preUminary experiments was found 

 to depend upon oxygen concentration. In Fig. 2 the magnitude of the 

 bursts is compared under different oxygen concentrations available 

 with convenient gas mixtures. The maximum of the burst appears to 



* Original records are shown wherever possible but tracings are used whenever 

 intercomparison of two or more records is required. 



