This slide shows a cross section of a stained, male, large intestinal roundworm (Ascaris lumbricoides). This nematode is a common parasite of humans, with over a billion people infected worldwide.  The section shows the outer protective cuticle secreted by the underlying hypodermis.  Longitudinal muscle bands, dorsal and ventral nerve cords, lateral lines (containing the excretory canals), the intestine and pseudocoelom (body cavity) are also visible. The slide also contain various sections through the long, coiled testis and vas deferens, the latter of which contains the ameboid spermatocytes (sperm cells).  Note: These structures may differ in shape, depending on the way they were sectioned.