Anatomische untersuchungen an Calyptostomiden (acari, trombidiformes). - In mites of the species Calyptostoma velutinus (Muller, 1776), ventriculus and ceca are composed of only one type of epithelium cells. The excretory organ is branched out and goes parallel to the ceca. A communication between ventriculus and excretory organ could not be proved. - One tubular and four acinous glands discharge into the podocephalic canal. The tubular gland consists of sacculus and tubulus. The podocephalic canals of both sides join. A tracheal gland is absent. - The lobed testicles communicate by a median lobe. A germinal stratum can be distinguished from a glandular part. The cavity of the testicular lobes serves as a reservoir for sperms and three types of secretions. There are no accessory glands or organs apart from two pairs of genital succers which are found in the progenital chamber. - In the female, similar genital succers are present. There was found an organ which is supposed to secrete fatty material. The eggs are produced following the nutritious type in an unpaired ovary.