The haplophase of the life cycle ofStemonitis fuscais recorded and the method is described to study the haplophase activity of this myxomycete. In all stages of the haplophase the protoplast contains a vacuolar body which stains orangered with neutral red. The protoplast ofS. fuscadid not shed a membrane any time after emergence from the spore. Various sizes of myxamoebae were discovered and syngamy is described.