C. elegans

C. elegans is a model organism that belongs to the nematode family and are transparent worms that live in neutral soil. They are usually around 1mm in length and are used extensively in research.

They are unsegmented creatures that have a bilateral symmetry. They use bacteria growing on decaying substances as a nutrient source. 

They have no female sex but are either male or hermaphrodites. This is determined by the number of sex-chromosomes to autosomes. If it is 1:1 then the worm is a hermaphrodite but if it is 1:2 it is male. C. elegans reproduce by laying eggs (laid by the hermaphroditic worms) and can lay up to 1000 eggs, although the average is ~ 300 eggs. However, if a hermaphrodite mates with a male, there can be as many as 1,400 offspring.