This is a comprehensive treatise on meiobenthology, the science of small animals which live, often disregarded even by zoologists, in huge numbers in all aquatic sediments. Covering all the scientific literature on the subject, particular emphasis is placed on ecological and systematic aspects. After a survey of the biotope conditions and important methods, the animals are introduced in a systematic account. This is followed by a report on the meiobenthos in relevant biotopes. The book concludes with an analysis of the productive role and the position of meiofauna in the food web and perspectives for future research.