Earthworm

Earthworm is the common name for the largest members of Oligochaeta (which is either a class or subclass depending on the author) in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female. Theoretical cladistic studies have placed them instead in the suborder Lumbricina of the order Haplotaxida, but this may again soon change. Folk names for the earthworm include "dew-worm", "Rainworm", "night crawler" and "angleworm" (due to its use as fishing bait).

Earthworms are also called megadriles (or big worms), as opposed to the microdriles (or small worms) in the families Tubificidae, Lumbriculidae, and Enchytraeidae, among others. The megadriles are characterized by having a distinct clitellum (which is much more obvious than the single-layered one of the microdriles) and a vascular system with true capillaries. 

Earthworms are hermaphrodites: They typically have two pairs of testes, surrounded by 2 pairs of testes sacs. There are 2 or 4 pairs of seminal vesicles which produce, store and release the sperm via the male pores, and ovaries and ovipores in segment 13 that release eggs via female pores on segment 14. However, most also have one or more pairs of spermathecae (depending on the species) that are internal sacs which receive and store sperm from the other worm in copulation. Some species use external spermatophores for transfer instead. 

Digestion

There is a digestion system in an earthworm. The process of nutrition begins in the mouth, where food is sucked in by a muscular pharynx. From there, food goes down the esophagus through peristalsis(muscle contractions.) After this, the food is stored in the crop, which retains food and has the ability to expand. From there, food goes into the gizzard where sand and muscular contractions churn the food and increase the surface area. From there, food enters the intestine which has the ability to absorb food, then food exits through the anus. A rectum is unnecessary because an earthworm is in a moist environment and thus does not require water 

http://en.wikipedia.org/wiki/Earthworm