Macrostomorpha taxonomy and phylogeny

The penis stylet is hook-shaped; it is slightly bent in another plane at a point indicated by the arrow. Its walls are not thickened at any particular point. Its distal opening is terminal. p. 53

The penial tube has a slight bend at its proximal end, and a distinct and sharp bend at its distal end. The distal tip of the stylet is blunt with a terminal opening. The walls appeared of uniform thickness along the length of the tube. p. 56

Eyes 13 x 25 micrometer. The penis stylet is bow-shaped, gradually tapering in diameter towards the swollen distal end. The walls of the distal end are slightly thickened; the distal opening is displaced slightly to one side of the swollen end and is not exactly terminal. p. 55

The distal opening is terminal and oblique, facing the concave side of the bow. The walls surrounding the distal opening appear to be very slightly thickened. p. 50

The penis stylet is a more-or-less straight tube which diminishes in diameter towards its distal tip; in fact the latter is slightly bent as shown in Figs. 5Band C. The walls of the tube around the distal terminal opening are slightly thickened. p. 54

Eyes 8 x 9 micrometer. The distal end of the penis stylet is bent so that the angle between this and the main axis is slightly less than a right-angle. The distal opening is oblique. The walls of the tube are of even thickness. A distinctive notch is present in one of the walls near the proximal opening (D). p. 54

Eyes 10 x 21 micrometer. The penis stylet is typically in the form of a blunt hook. The walls of the tube around the distal terminal opening are very slightly thicker than the walls in the remaining part of the stylet. p. 52

With bean-, cycle-, kidney- or long kidney-like eyes. The end of penis is spinous, twisting vertically from penis plane. p. 720