Cell mixtures of different species and strains of cellular slime moulds.

INTRODUCTION T H E cellular slime moulds have, in their life history, a period of feeding of separate independent amoebae which subsequently stream together (by a process involving chemotaxis) to central collection points. Each of the resulting cell-masses differentiates into a fruiting body; in most species there is a delicate tapering celluose stalk which surrounds the large vacuolate stalk-cells, and an apical sorus containing a considerable quantity of individually encapsulated spore-cells. There are a number of distinct and easily recognizable species and, moreover, it is a common observation (see Raper, 1951) that different isolates from the soil of any one species may have small but identifiable characteristics. It was found, for instance, in a previous study (Bonner & Shaw, 1957) that some strains under given environmental conditions formed a very long stalk, that is, delayed the process of spore differentiation, while others show rapid spore differentiation and correspondingly short stalks. The purpose of this study was to examine the effect on the morphogenesis of these slime moulds of mixing the cells of different species and different strains in various ways. Such experiments show that there are varying degrees of compatibility among the combinations and that in many cases there are interesting types of compound fruiting bodies. Also it will be demonstrated that cells of a particular strain when disassociated tend to regroup within the cell-mass and certain parallels will be drawn between these results and those of sponge and otheranimal cell-dissociation experiments.