SummaryThe more important features in the morphology of the male urogenital system ofLepitlosirenandProtopterusmay be summarized as follows:—1The testis is very much elongated and is divisible into an anterior formative and n posterior vesicular and conducting region.2The posterior part of the vesicular region is connected with the tubules of the hind end of the mesonephros, which serve for the passage of the genital products.3InProtopterusthe testis is connected with the kidney only at its extreme tip; inLepidosirenthere is a stories of about half a dozen segmentally arrangedvasa efferentiawhich open into Malpighinn capsules.4InProtopterusthe hind genital region of the kidneys is clearly marked off from the rest, and in this region the kidneys are fused across the middle line; inLepidosirenthere is only a slight attempt at this differentiation, and the kidneys of the two sides are posteriorly, as elsewhere, quite distinct.5The Wolffian ducts open in the adult inale by a common (Protopterus) or by two separate (Lepidosiren) papillae into the distal portion of the cloacal caecum, which is morphologically a urogenital sinus formed in ontogeny as a dilatntion of the fused, but originally separate, posterior portions of the Wolffian duct