452 WINTERTON C. CURTIS, 



the duct never found in the condition of a solid rod of cells. The 

 continuity has been demonstrated in the following way. In longitudinal 

 series the portion of the duct found in each section was carefully 

 drawn with a camera at its proper place after the manner shown in 

 PI. 31, Fig. 7. The results were afterwards transferred to a slip of 

 paper and the entire tube thus represented by a series of short lines 

 each giving what appeared in a single section. These lines were 

 numbered to correspond with the section where they were found and 

 the duct shown to be continuous from the seminal vesicle at its 

 posterior end to the most anterior testes. I have applied this method 

 to worms taken at different times and am certain that during the 

 months in which specimens were examined the vas deferens is con- 

 tinued forward without any breaks. Moreover the testicular canals 

 were found in all the worms where an attempt was made to follow 

 them and specimens thus examined extend over the whole period. 



The seminal vesicles (PL 31, Figs. 1 and 8 sv) are simple enlarge- 

 ments of the vasa deferentia in no wise different from the smaller 

 ones sometimes found higher up (PI. 31, Fig. 1 en). They are some- 

 what convoluted and bend around behind the pharyngeal apparatus 

 with a sharp decrease in diameter as they near the mid-line. Where 

 the two unite at the base of the penis there is a slight enlargement 

 {e) surrounded by a tangle of muscle fibres, similar to that described 

 by Ijima ('84, tab. 21, fig. 5, p. 408), which is the only point at 

 which there is any trace of musculature in connection with the male 

 ducts, except that around the penis lumen. The lining of the seminal 

 vesicles and vasa deferentia (PI. 31, Figs. 5 and 6 vd) is a definite 

 epithelium with no cell outlines apparent and the same in appearance 

 as that of the finer canals or certain portions of the testicular epi- 

 thelium (PL 32, Fig. 10). The nuclei (w) are characteristic being oval 

 in shape and showing a granular arrangement of the chromatin by 

 which they are easily distinguished from those of the surrounding 

 parenchyma. 



The penis (PL 31, Figs. 1 and 8 p) is plug-shaped almost filling 

 the atrium and extends into that cavity without a secondary sheath 

 of a ny kind, in exactly the same way as the pharynx into the pha- 

 ryngeal pocket. Its lumen derived from the enlargement at the meeting 

 of the two seminal vesicles is of uniform diameter and lined with 

 small cuboidal cells (PL 31, Fig. 3 l) similar in appearance to the 

 larger cells lining the atrium (aep) with which layer they are con- 

 tinuous through the flattened epithelium covering the penis (ep). While 



