3NOTES in predictability of the survival time; the concentration of parasites in peritoneal exudates varies enough from one group of mice to another that one either must use two dilutions every week, doubling the number of animals expended, or else be prepared to deal with an unpredictably variable time of death, ranging from 5 to 10 days as a rule.

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Unusually high numbers of pigmentless variants and sectored colonies in cultures of lyophylized Serratia marcescens are reported. Clonal analyses of sectored colonies show the presence of unstable bacteria that continue to sector again when plated. Further analysis of pigmentless variants suggest that pigment formation, oxygen uptake, and the production of an inducible protease are affected.

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