RESUMO
The dart of Eremina ehrenbergi is a small white delicate structure. It consists of funnel-shaped corona with two blades; a short flare and an extended shaft which is surrounded by two lateral vanes. Dart formation was investigated by examining the histological structure of the dart sac of snails before and after copulation. Dart sac is a finger like muscular protrusion. Its internal epithelial lining forms at its blind edge an extended tubercle which gives its lumen a Y-shape. Dart formation begins at the tip of the tubercle in which the epithelial cells secrete a crystallite and homogeneous material which forms the mineralized part of the corona. The subsequent secretory activity of the tubercle epithelium results in an increase in the diameter and anterior lengthening of the corona and the flare. The continued secretory activity of the dart sac epithelium forms the layers of the shaft and the lateral vanes. The fine sculpturing structure of the dart had been investigated by using SEM.