This is the first and so far the one and only treatise on the morphology of the Tylenchs. Tylenchs are economically important Nematodes that live in huge numbers in the soil. They are microscopic and they show a constant number of cells, a characteristic in Nematodes. The cell count in Tylenchs, undertaken here for the first time, resulted in an estimate of fewer than a thousand cells. All the different cell types are described in great detail, and some of them are rather unusual in the Animal Kingdom. The internal pressure system (typical for Nematodes) in conjunction with the presence of a hollow stylet (typical for Tylenchs), results in rigorous but functional relations among the several body parts. Throughout the book functional morphology is a key topic and an entire chapter is devoted to it. The book is amply illustrated with line drawings that are based on microscopic and sub-microscopic observations.