Fig. 4. Sections of cells cultured anaerobically in the dark for 96 hours at 30'', 

 gassed with 5% CO2 in N2 (residual O2 : 0-036",,) at a rate of 35 to 40 ml. of gas 

 per hour (cf. Fig. 14, ref. [3]). The bacteriochlorophyll content at the end of the 

 period of 9-5 fig. per /xl. of packed cells. The culture had been derived from an 

 inoculum of almost colourless aerobically dark-grown cells which contained 0-024 

 /xg. of bacteriochlorophyll per /A. of packed cells. The section of the anaerobically 

 cultured cells shows abundant and distinct chromatophores (C). Magnification as 

 indicated for Fig. 6. 



Figs. 5 and 6. Sections of cells cultured for 66 hr. aerobically in the dark at 

 30° (cf. Fig. 9, ref. [31]). The cultures were gassed with 5^0 CO2 in air; the gassing 

 rate was somewhat slower than indicated in the text and synthesis of a small 

 amount of chlorophyll had taken place. A few scattered chromatophores (C) are 

 apparent in some of the cells. A lamellar system (L) of unknown composition and 

 function (cf. Figs. 21-25, ref. [3]) also can be observed. 



