A method and apparatus for performing assays in a single step which does not require the user to perform a washing step, does not require the user to add any reagent or other solution other than analyte sample fluid to the apparatus, and does not require the user to come into contact with the apparatus at any point during the assay procedure after the fluid suspected of containing a particular ligand is added to the apparatus. The apparatus for performing the assay consists of a single container with at least three ports disposed through different planes in the body of the apparatus beneath which labelled antiligand (the first port), unlabelled antiligand (the second port), and unlabelled ligand (the third port) are disposed. Said labelled antiligand is complementary to both the analyte of interest and the unlabelled ligand, the latter of which serves as a control display for comparison of any color changes mediated by the label visible through the second port. The antiligands and ligands disposed beneath each port are bound to separate membranes. At least the first membrane is bibulous and is disposed at one end of a ramp where, at the top of which, it overlaps the second membrane thus slowing the flow of sample and improving the performance of the assay.