1905.] NATURAL SCIENCES OF PHILADELPHIA. 387 



duct and diffuse prostate gland of Monopylephorus with the soft penis 

 having a thin cuticular sheath of a typical Tubifex. Large funnels 

 open into X on each side near the body floor and, after perforating the 

 septum in line with the ventral setse, pass into short wide vasa deferen- 

 tia which bend laterally and gradually expand into the long sperm 

 reservoirs constituting at least one-half of the entire duct. Near 

 the posterior end of the somite they bend abruptly upward to a point 

 above the intestine, and, by a short constricted region, pass into the 

 summit of the penis sac, which is nearly vertical but curves forward 

 to the external pores. The penis sac is cylindrical and has a thick 

 muscular coat; the free penis begins at about its middle, but is usually 

 considerably folded within the lower part of its cavity. There is a 

 distinct but thin cuticular lining reflected on to the penis. The prostate 

 gland is a thick layer of cells, especially enlarged on the dorsal side, 

 uniformly covering the entire sperm reservoir. 



The sperm sacs and ova sacs are quite similar to those of Monopy- 

 lephorus glaher. When fully developed the anterior sperm sac reaches 

 through IX, the posterior to XV and the ova sac to XXII. The pos- 

 terior sperm sacs are originally paired and in immature worms may be 

 seen to be swept back and forth, alternately reversing and righting 

 themselves, with the movements of the ccelomic fluid. 



It is certain that this is one of the species included by Prof. Verrill 

 in his Clitellio irrorata, and a few specimens are included among those 

 so labelled. As no type is indicated, it seems perfectly proper to pre- 

 serve the name by applying it to this, rather than to permit it to lapse 

 as a synonym of one of the species already named, even though tlie 

 latter chiefly influenced the original description. 



Like M. glaher this is a brackish water species, and the two are fre- 

 quently found associated about the outlets of littoral springs where an 

 accumulation of organic mud makes the conditions otherwise favorable. 

 The remarks under M. glaher concerning acclimatization to fresh and 

 salt water apply equally to this species, which is, however, much less 

 resistant to unfavorable circumstances than that species. Perhaps 

 this fact accovmts for its much less abundance, though its habit of 

 burrowing more deeply into the soil among the roots of beach grass, 

 in the smaller rootlets of which its peculiar capillary sette become 

 twisted, make it much more difficult to find. Sexually mature indi- 

 viduals constitute a much smaller per cent, of those found than in M. 

 glaher. So far as now known this species occurs only south of Cape 

 Cod. 



