The Ascaris Lumbricoides, or Round Worm, is one of the biggest nematodes in their phylum that infect themselves in humans. Like most other Nematodes, the Round Worm has no circulatory system. It uses diffusion, just as most other nematodes do, in order to transport oxygen through and around their bodies.
The Round Worm has two sexes. Each sex is, of course, similar, but small physical characteristics vary. The female Round Worms are significantly bigger than the males. The females can be anywhere from 20 to 50 centimeters long, while the males can only get as long as 30 centimeters. Both sexes are beige in color, and have bodies that taper at each end. The structural appearance and biological make up of the Ascaris Lumbricoides is quite interesting.