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http://shreeya-biologyworld.blogspot.com/2012/01/balanoglossus-excretory-system.html

The glomerulus present in the proboscis is considered as excretory organ of Balanoglossus although experimental evidence is lacking. The peritoneum which covers the proboscis complex gives off a number of finger-like outpushing into proboscis coelom. They are arranged around the tip of the buccal diverticulum. The peritoneal lining of these evaginations is composed of cuboidal, columnar or conical cells. These cells proliferate to form masses which fill the spaces between the evaginations. These cells stain very poorly and contain very small quantity of cytoplasm.

All the blood collected by the dorsal vessel is poured into the glomerular evaginations. Here the nitrogenous waste products are removed from the blood are passed on into the surrounding probasuidal coelomic fulid before it is passed on into general circulation. The urea and uric acid thus extracted from the blood are passed on into the surrounding proboscidal coelomic fluid from where it is excreted through the proboscis pore.

http://biology-today.com/general-zoology/invertebrate-zoology/excretory-system-in-balanoglossus/