288 inifwis State Laboratory of Natural History. 



Fridericia agilis u. sp. 



Numerous specimens of an encln'trpeid worm belonging- 

 to the genus Fridericia were found at Havana, 111., asso- 

 ciated with the different species of Diplocardia. They 

 were sexually mature in April and May. 



The length of well-extended living specimens is 25-30 

 mm. and the number of somites is 57-66 in the specimens 

 examined, the average number being 62. 



The setae are straight, with the exception of a slight 

 curvature of the proximal end, the usual number in each 

 bundle being two, although sometimes one or even two 

 additional may be present in a few of the bundles, 

 Occasional specimens are found in which between the 

 ordinary setae of a pair a second pair of very slender ones 

 is present, the diameter of the latter being one half that 

 of the former, or even less. In such specimens this ar- 

 rangement of setae prevails posterior to the clitellum 

 as well as anterior to it. A head pore is present between 

 the prostomium and peristomium, and the first dorsal 

 pore is in VII. The clitellum is on XII and XIII. 



The posterior margin of the brain is quite convex,, 

 while its anterior margin is slightly concave. Its length 

 is one and a half times its greatest width, and the 

 posterior part is a little wider than the anterior. The 

 salivary glands are large and very much branched, and 

 open into the alimentary tract between its lateral and 

 ventral walls in somite III. Septal glands occur in IV, 

 V, and VI. The anteseptal part of each of the nephridia 

 equals the postseptal part in size. The duct of the 

 former is convoluted, and the terminal duct arises from 

 the posterior end of the postseptal part and opens in 

 front of the ventral setae. The dorsal vessel arises in 

 XIX. The spermathecae communicate with the aliment- 

 ary tract, each of them having about nine well-developed 

 diverticula, which are hollow and somewhat unequal. 

 The duct, which is about three times the length of the 

 pouch, is slender, cylindrical, and without glands, excepti 



