214 Description of the Plates. 



tion. The outer row of setae is often wanting' in the anterior 

 segments; in the others it is usually connected with the 

 inner row by a transverse muscular slip, such as that seen 

 here^ or at e 2. In the region of the clitellus the outer row 

 of setae may he adapted to serve as accessory copulatorj 

 organs ; elsewhere they are purely locomotor. 



/%. Inner row of setae. The spines are solitary in their inser- 

 tion as in the outer row, but they are in many segments, as, 

 for example, in the tenth and fifteenth, besides the segments 

 constituting" the clitellus, modified so as to serve as organs 

 of adhesion. 



g I . Anterior receptaculum seminis of the left side, opening in 

 the interval between the ninth and tenth segments, and 

 between the lateral and dorsal muscles in the line of the 

 outer row of setae. 



g 2. Posterior receptaculum seminis, opening in the interval 

 between the tenth and eleventh segments. These organs 

 are very variable in size, and have had their existence over- 

 looked and denied. Their outer opening is marked by a 

 small elongated papilla; but their development is not 

 always exactly correlated \vith that of the rest of the gene- 

 rative apparatus. 



hi. Anterior vesicula seminalis of the left side, attached to the 

 posterior dissepiment of the ninth segment, and communi- 

 cating, as does the middle vesicula seminalis 7i 2, with the 

 anterior compartment of a sac with delicate walls which 

 occupied a space in the tenth and eleventh segments cor- 

 responding to that underlaid by the azygos ventral muscle, 

 and received the openings of the vesiculae of both sides. 



7i 2. Middle vesicula seminalis of left side. 



^3. Posterior and largest vesicula seminalis, opening into the 

 posterior compartment of the azygos central atrial sac just 

 described. 



ii. Funnel-shaped orifice of vas deferens anterior of left side. 



12. Similar orifice of vas deferens posterior of left side. 



^3. Similar orifice of vas deferens anterior of right side. 



?'4. Similar orifice of vas deferens posterior of right side. Ex- 

 ternally and interiorly to each of these infundibula there 

 exists in each of these segments a segmental organ's 



