Excretory system of Earthworm
- The excretory system of earthworm consists of segmentally arranged coiled tubes called nephridia
- The major function of nephridia is to regulate the volume and composition of the body fluids
- A nephridium starts as a funnel which collects excess fluid from coelomic chamber
- The tubular part of the nephridium delivers the wastes through a pore to the surface in the body wall into the digestive tube
- The nephridia are of three types i.e. pharyngeal nephridia, integumentary nephridia and septal nephridia
Integumentary nephridia
- These are V-shaped nephridia attached to the lining of the body wall of segment 3 to the last which open to outside through nephridiopores
- These nephridiopores are minute openings present on the body surface.
Septal nephridia
- These are the largest nephridia in earthworm
- These are arranged along the sides of the intersegmental septum from 15th segment onwards
- These open into the intestines
Pharyngeal nephridia
- It is present as three paired tufts in the 4th, 5th and 6th segments on either side of the pharynx and oesophagus
- They open into buccal cavity and pharynx

Hence, the correct option is (b).
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