Japanese Tricladida Maricola. 



81 



it there exists a muscular layer of circular fibres which are more 

 well developed in the part of tlie ejacuLatory duct tlian in the part 



Text ûg. 4. Di agram Diatic eopulatory organs of Procerodes 

 lactea iu sagittal fectiou. 



de ductus ejaculatorins, cjl gland, v vagina. 

 Other letters as in text figs. 1 and 3. 



of the vas deferens impar. Besides, the minute structure of the 

 intromittent part shows no difference in any essential respects, 

 'from what has hitherto been described. As usual, the penis is 

 externally covered with a thin layer of normal cells, which is con- 

 tinuous with the lining epithelium of the penis-sheath, while in 

 UcL Umuli the epithelium is devoid of nucleus at all. Im- 

 mediately beneath the epithelium there exist two muscular layers 

 of strongly developed circular and longitudinal fibres. Between 

 the external and the internal muscular layer there is a zone of a 

 mass of the connective tissue, which is traversed by feeble radial 

 muscular fibres. A number of nuclei regarding as either myo- 

 blasts or nuclei of the connective tissue lie arranged directly below 

 the external muscles. These, I beheve, for the most part, to be 

 >cells that have produced the muscular fibres. The penis bulb 



