Abstract
SUMMARY Measurements of individual generation times were carried out on three species of bacteria, each in two different growth media. They confirmed in every respect conclusions already reached about the broad features of the generation time pattern. In addition, they supported two important inferences the existing evidence for which was no more than suggestive: (i) complex media give rise to a greater dispersion of generation time than do simple media; (ii) there is positive association between the generation times of second cousins, i.e. organisms whose nearest common ancestor is three generations removed.