Abstract
Using staphylococci grown from single-cell isolations made at various stages of selection on penicillin media, the 18-hr. progeny showed variations in penicillin sensitivity, as tested by increase in resistance. The range of variation was about the same at any stage in selection; variation appeared to be continuous in any one pop. of the microbes, since the no. showing increased resistance depended on the closeness of the steps in penicillin concn. used in testing the resistance.

This publication has 4 references indexed in Scilit: