Abstract
The ductus ejaculatorius simplex (simplex) of the reproductive tract of the adult male of Calpodes ethlius is separated by distinct constrictions into seven segments, varying in length from 0.24 to 19.3 mm and totalling 4 cm. Two of the segments, S1 and S5, are further divisible into three and two parts, respectively, on the basis of either cellular structure or secretory products. The most distinctive region is the most anterior one which is made up of two distinctly different cells, one a merocrine secretory cell which resembles the cells of all other regions, and the other an apocrine secretory cell whose highly modified apical region is sloughed upon copulation. All segments are surrounded by two layers of muscle, a thin, inner circular layer and a more robust, outer longitudinal layer, which are supplied with tracheoles and nerves. Tracheoles also penetrate the epithelium of segment seven. The merocrine secretory cells of all segments are similar in that they all have well-developed endoplasmic reticulum, numerous Golgi and mitochondria, and a microvillate apical surface. Nonetheless, the cells of each segment are distinguished by some feature of either their structure or their secretions.