The trophic stage is amoeboid and aflagellate, possessing filose pseudopodia during locomotion. In culture, once the food supply is exhausted, the amoebae can aggregate under the influence of chemoattractants to form a pseudoplasmodium. The pseudoplasmodium is an aggregation of individual amoebae that differentiate into pre-stalk and pre-spore cells. The pseudoplasmodium may or may not migrate extensively, but ultimately undergoes soro-genesis, during which a stalk tube is formed by the stalk cells which, in the Dictyosteliidae become incorporated into the stalk tube. The remaining amoebae go to the top of the stalk tube, secrete a wall and become spores. The mass of spores is referred to as a sorus. A slime sheath covers the entire sorocarp. Under appropriate conditions, amoebae of some species can fuse to form a diploid cell that becomes a macrocyst, wherein meiosis occurs.