The aggregate forms an apical tip and then elongates to an extended, finger-like structure of approximately 1 or 2 mm. The finger eventually falls over and begins to migrate similar to a miniature slug orienting towards light. Migration occurs in the range of centimetres. The slugs leave a slime track consisting of extracellular matrix behind. This trail solidifies and builds a solid fibre network which may connect several slugs which have crossed trails. Under certain conditions the slug stops migration, forms the "Mexican-hat-structure" and begins culmination.

Within the aggregate, cells have initiated differentiation into essentially two cell types: cells in the tip and later in the anterior 20% of the slug have become prestalk cells with a typical gene expression pattern while the 80% of cells in the rear have taken the prespore pathway. Within the posterior prespore mass, approximately 10% of cells have anterior-like characteristics.

During culmination, prestalk cells migrate downwards through the prespore mass in the manner of an inverted fountain. They vacuolize during this process and form a rigid stalk. The prespore cells are thus lifted up from the substratum. They shrink and synthesize a solid spore coat which makes the durable spore resistant to heat and other kinds of environmental insults. The final fruiting body is about two millimetres high and consists of a thin stalk of dead, vacuolized cells supporting a spherical spore head.

Dictyostelium is undoubtedly an excellent model system to study biological problems of general importance. Among others, these cover the fields of cell motility, signal transduction, cell differentiation, pattern formation, phagocytosis, chemotaxis, cell communication etc. Within the last 15 years, essentially all molecular tools have been developed for Dictyostelium. These include transformation with integrating and extracellular vectors, marker genes like GFP, b-galactosidase and b-glucoronidase, gene knock-outs by homologous recombination, gene inactivation by antisense gene constructs and a powerful mutagenesis system (REMI) which allows for the easy isolation of the mutagenized gene.