Pharyngeal nephridia occur in three pairs of bunches in the 4 th, 5 th and 6 th segments lying on each side of the alimentary canal. The ducts of the nephridia of the sixth segment open into the buccal cavity while the ducts from the nephridia bunches of the fourth and fifth segments open into the pharynx. These ducts carry excretory products from the pharyngeal nephridia into the gut. Enteronephric condition is an adaptation for the conservation of water which is absorbed by the inner lining of the alimentary canal.
Ectonephric nephridia discharge their contents directly to the outside which help the earthworm in keeping the skin moist for cutaneous respiration only. Integumentary nephridia are ectonephric nephridia while, pharyngeal and septal nephridia are enteronephric.