There are two sexes in this organism: a self-fertilizing hermaphrodite and a male.  
There are two sexes in this organism: a self-fertilizing hermaphrodite and a male.  The adult essentially comprises a tube, the exterior cuticle, containing two smaller tubes, the pharynx and gut, and the reproductive system all within a one-millimeter package.  All 959 somatic cells of its transparent body are visible with a microscope, and its average life span is a mere 2-3 weeks.  Perhaps the most interesting thing about this nematode, though, is its 97-million base pair genome.  FTP, identify this worm, the second eukaryote after budding yeast to have its genome completely sequenced.
There are two sexes in this organism: a self-fertilizing hermaphrodite and a male.  
Caenorhabditis elegans