In which one of the following organism, its excretory organs are...

In earthworm, excretory system is made up of many segmentally arranged microscopic coiled tubes called nephridia. These are ectodermal in origin and analogous to vertebrate kidney. In Pheretima, following three types of nephridia are seen. (i) Pharyngeal nephridia-Situated in either side of pharynx and oesophagus in $4^{\text{th }}, 5^{\text{th }}$ and $6^{\text{th }}$ segment. (ii) Integumentary nephridia-Scattered in the body wall, seen from $7^{\text{th }}$ segment onwards. (iii) Septal nephridia-Largest nephridia attached to both faces of each intersegment septum behind $15^{\text{th }}$ segment.