Primary homology assessment in the male atrial system of the Polycystididae (Platyhelminthes: Eukalyptorhynchia)

A comparative lightmicroscopical study of the male atrial system of the Polycystididae is presented. Firstly, the different glandular structures associated with the male atrial system are compared. This has lead to the recognition of eight different types of glandular vesicles, four of which are considered prostate, the other four accessory. Secondly, the different hard structures that can be found in the male atrium are discussed and compared. These hard structures can consist of numerous hard spines (armed cirrus), but mostly the hard structure is a single- or double-walled tubiform stylet, or a plate-shaped stylet. Different types of stylets can be recognised, some of which are associated with a prostate vesicle and therefore considered prostate stylets. Using the criteria of position and conjunction, conjectures of homologies are put forward. These primary homologies are compared with homology assessments found in earlier literature.