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Most of these compounds were isolated from cultivated representatives of only five bacterial groups: filamentous actinomycetes, Myxobacteria, Cyanobacteria, and members of the genera Pseudomonas and Bacillus.

If on the one hand the Myxobacteria are certainly schizomycetes, on the other they just as certainly offer in their developmental history "phenomena closely resembling those presented by plasmodia or pseudo-plasmodia...."

The Myxobacteria are most easily obtained by keeping at a temperature of 30-35� C. in the dark dung which has lain exposed to the air for at least eight days.