Macrostomorpha taxonomy and phylogeny

The penis-stilette is a lengthy, tubular structure containing two right angle bends in its main axis. The basal proximal rim is dentate. The enlarged end is quite asymmetrical in that one side wall is always longer and larger than the other one. The sperm cell has a feeler, a conspicuous anterior swelling, lateral paired setae, but lacks a definite tail region. This cell lacks observable chromatin granules. p. 275