Nitrogenous waste is excreted in the form of ammonia through the body wall, and is not associated with any specific organs. However, the structures for excreting salt to maintain osmoregulation are typically more complex. 

In many marine nematodes, there are one or two unicellular renette glands that excrete salt through a pore on the underside of the animal, close to the pharynx. In most other nematodes, these specialised cells have been replaced by an organ consisting of two parallel ducts connected by a single transverse duct. This transverse duct opens into a common canal that runs to the excretory pore. 

It is thought that most actual excretion occurs through the intestine and that the so-called excretory systems were named as such based merely on their morphology and before definitive functions were identified.  Most excretory systems appear to have secretory and osmoregulatory functions and can be termed S-E systems. 

Two basic types of S-E systems exist: glandular and tubular.  Most free-living nematodes have the glandular type while the tubular type is commonly found in the parasitic nematodes.

This is the excretory pore.  Its location is species specific and serves as a taxonomic character. 

Water and ion excretion are poorly understood in nematodes.  The S-E systems seem to be involved in water excretion, but the details remain mysterious. 

Ammonia is the major nitrogenous waste product of nematodes.  Urea is a lesser component of the nitrogenous wastes.  Amino acids, peptides, and amines may also be excreted by nematodes.  Other types of excretory products include carbon dioxide and several fatty acids.  The cuticle is also thought to play a role in ammonia secretion in most nematodes. 

- Wind God "Tengu Throwing Stones"
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