ABSTRACTThe ultrastructure of the flagellar apparatus ofSemimorula liquescenswas determined using serial section analysis to assess the taxonomic position of this species within the Eumycetozoa. There is not a close association between the flagellar apparatus and nucleus. One of the flagellar components is the anterior, posterior and procentriolar complex. The anterior centriole gives rise to the single, anterior whiplash flagellum. A para-kinetosomal structure associated with the posterior centriole is attached to a non-striated connective that wraps around the anterior centriole. Each flagellar apparatus contains microtubule arrays 1–5. A convoluted, shelf-like MTOC is attached to the anterior centriole. Because the flagellar apparatus ofS. liquescensis basically identical to that of the Myxomycetes, an affinity with this group of Eumycetozoa is evidenced.