3o8 CALIFORNIA ACADEMY OF SCIENCES. 



ment towards an ancestral form, and that a single sperm 

 duct with a single rosette is the characteristic and usual 

 feature of the genus. 



Prostates (figs, i, 23, 25 and 26). There are four pros- 

 tates, two on either side, or two opening in each of the 

 genital zones, one in the anterior angle of the crescent 

 and one in the posterior. The prostates are short or 

 about as long as the somite is wide, but they are much 

 bent and generally do not extend much across the ventral 

 ganglion, except when violently extended, when they 

 would reach across the ventral side of the body. Their 

 exact length, however, varies and one prostate is generally 

 a little longer than the other. As in the allied genera we 

 may distinguish a muscular and a glandular part of the 

 same general nature as in Ocnerodrilus. The glandular 

 part consists of only one layer of glandulous cells. The 

 muscular part varies in size, and is generally of unequal 

 length in the anterior and posterior prostate. In the 

 two specimens which I dissected the muscular part of 

 the anterior prostate was much longer than the muscular 

 part of the posterior prostate, and in one specimen the 

 muscular parts of both prostates were proportionably 

 longer than in the other. I presume that there is consider- 

 able variation in relative size of these parts and that too 

 much importance must not be placed on a longer or 

 shorter prostate. Still the variation is probably within 

 certain limits and may prove to be of value in characteriz- 

 ing the species as we know that in the various species 

 of Ocnerodrilus, the relative length and width of the 

 muscular and glandular part of the prostate is of 

 great importance as species characters. In Kcrria 

 McDonaldi the glandular part of the anterior prostate 

 was found to be about three times as long as the mus- 

 cular part, while the glandular part of the posterior 



