246 CALIFORNIA ACADEMY OF SCIENCES. 



While forming one single tube as far as their outward 

 form is concerned, they still remain separated, the ciliated 

 lumen of each being readily visible even close to the 

 papillae (fig. 57). The absence or presence of a enlarged 

 and differentiated lower part of the sperm ducts is of the 

 greatest importance as a species characteristic. A similar 

 modification of the sperm duct is found in Pygmaeodrilus. 

 T\\^ prostate gland is smaller than in most other species, 

 except in Ocnerodrilus guatemalce. In Ocnerodrilus occi- 

 de7italis it passes from somite xvii to xxiv, or further 

 yet; but in Ocnerodrilus Beddardi it occupies only two or 

 three somites, and in Ocnerodrilus guatemalce only one. 

 It is bent several times on itself (in this there is no con- 

 stancy) and ascends first upward. The inner epithelial 

 lining consists of only one layer of tubular cells similar as 

 in the other species and as in Gordiodrilus. 



There exists in the prostates of the various species two 

 more or less differentiated parts. Generally there is an 

 upper only glandular part and a lower part which is 

 muscular and which connects with the male pore. In 

 these species, Ocnerodrilus sonorce and guatemalcB, this 

 lower part is much less differentiated, containing tubular 

 glandulous cells, and this part of the prostate differs only 

 in the addition of two muscular layers. In the other 

 species the muscular part of the prostate is much differ- 

 entiated and entirely void of the tubular glandulous cells, 

 so characteristic of the upper part of the prostate in all 

 the species. 



In Ocnerodrilus Beddardi the lower part of the prostate 

 is narrower, slightly tapering towards the purely glandular 

 part (fig. 55). In O. sonorce (fig. 59) the lower muscular 

 part is thicker than the upper glandular part, gradually 

 decreasing in size towards the distal end. The prostate 

 of O. guatemalce is only half as long and about one-third 



