5 



which does not stain, exactly like the basal-membrane of the radula. The purpose of this is 

 not clear. The basal-membrane, after leaving this pouch, does not become thicker, so that 

 increase of cuticular matter does not take place. Reparation of the basal membrane is possible, 

 as on its long course it may have become injured here and there. A strong circular muscular 

 layer surrounds the radu'a-sac, which is sustained by a few cartilaginous cells (fig. 1 6cc). 



On both sides of the radula a salivary gland o])ens into the pharyn.\. The salivary glands 

 are long, thick-walled tubes, running ventrally from the intestine. 



The part ne.Kt to the pharynx (the oesophagus, if at least this name may be used) is 

 very small and has a strongly folded wall. This together with the large fold in the ventral 

 pharyngeal wall, situated in front of the radula, renders it possible for the pharynx to be 

 evaginated with the radula. The wall of the oesophagus is ])uilt up of cubical epithelium with 

 thick cuticula. 



About the intestine there is nothing noteworthy. The lateral coeca are of very regular 

 size. Gradually the intestine merges into the rectum, the epithelium of which is ciliated at the. 

 dorsal wall. The transition into the cloaca, the wall of which is entirelv ciliated, is trradual. 



The generative glands are of normal structure. Both the genital products occur in a 

 mature state in one and the same specimen. They open out into the pericardium through two 

 ciliated ducts. 



For the course of the cloaca-ducts see reconstruction fig. i i : it is to be noticed in tliis 

 figure that only the intestine, generative organs, pericardium and cloaca-ducts are given, and 

 of the cloaca only that part, into which the rectum, opens out. The cloaca-ducts first take their 

 course proximall}', then bend and run distally to unite into the large precloacal organ (nidamental 

 gland, Schalendriise of Wirex, organe precloacal of Pruvot). The part of the cloaca-ducts 

 running proximally, which is not glandular, presents a peculiar structure. The portion, passing 

 out of the pericardium, is built up of epithelium-cells of unecjual height, the inner surface being 

 therefore undulated, these cells carry cilia (fig. i8 A). Farther on the duct widens considerably 

 and at different points the folds of the wall become so deep as to touch each other; so narrow 

 tubes are formed, running parallel to each other. Several of these tubes are compactly filled 

 with spermatozoa, very regularly placed with their heads directed towards the wall and their 

 tails directed inwardly. In these tubes the cilia have disappeared; only the median part of the 

 cloaca-duct preserves the cilia, amongst which there are a great number of strongly staining 

 granules (fig. i8B). Close to the point where the cloaca-ducts bend for the second time, they 

 narrow again and are reduced to their former shape. A pretty strong circular muscle surrounds 

 this part of the cloaca-ducts. It appears to me that this extension of surface should perform 

 the function of vesicula seminalis, whilst other appendages may be looked upon as receptacula 

 seminis. These consist of two spacious bags, connected with tiie cloaca-ducts by short canals. 

 In this there is affinity with Dondersia festiva (Hubrecht 3) and Ismenia ichthyodes (Pruvot 4). 

 The wall consists of cylinder-epithelium with oval nuclei at the basis, strongly ciliated. In these 

 bags numerous spermatozoa, disj)ersed in every direction, are found; for the rest I do not 

 consider a secretory function impossible. Copulation probably takes place : two strong copulation- 

 spicula are present. 



