Paragnath variation was examined in two populations of the epitokous form of the polychaete Perinereis cultrifera from the English Channel and the Algerian Mediterranean coast. Populations differ from each other in the mean number of paragnaths in groups I, II, III, V and VII–VIII, in the number of teeth per half jaw and in the morphology of paragnaths in the posterior belt. Individuals of the two populations studied share no common alleles at five loci involved in electrophoretic comparison. The general protein band patterns reveal 13 markers that discriminate between the Perinereis individuals. Congruence of all the reported results agree with the assignment that P. cultrifera is a complex of species, probably more than two.