EXTENSIVE investigations on the morphological changes during sporogenesis have afforded valuable information about this phenomenon1. The initiation of eporulation can be better understood if the metabolic events during the transition from a vegetative cell to its sporulating phase are known. Several attempts have been made to investigate the physiology of growth distinct from sporulation. Foster et al.2 found that when vegetative cells of B. mycoids were removed from the complex growth media before the point of maximal growth and transferred to distilled water, they formed spores. This was termed ‘endotrophic sporulation’. But experiments with B. cereus strain T (phage-resistant organisms) showed that ‘endotrophic sporulation’ can be observed only when granulated cells were suspended in a medium containing sufficient calcium ions3. (The shortening and granulation of cells are usually noticed only long after the cessation of growth.) Non-granulated vegetative cells lysed on transfer into a non-growth supporting medium. In this communication, we report observations which lend evidence to the presence of an ‘endogenous factor’ involved in the initiation of the morphogenesis in the vegetative cell leading to the formation of a granulated cell (Fig. 1) possessing the ability to sporulate in a medium which does not support growth.