Summary By means of the Saisawa-Sugawara silver deposition method it was demonstrated that the commoner blood and tissue microfilariae possess annular transverse cuticular striations that completely cover the embryos from tip to tip. Striated cuticulae were demonstrated on the Mf. of Wuchereria bancrofti, W. malayi, Loa loa, Mansonella ozzardi, Acanthocheilonema perstans, Onchocerca volvulus, Dirofilaria immitis and, with less certainty, on Litomosoides carinii. No embryo of the 8 species examined possessed a lateral or side line. These alleged lines, and the knobby ends of the striations, were demonstrated to be optical artifacts.