55 



MESENCHYTR^US PEDATUS sp. nov. 

 (pi. i, figs. 13 and 14 ; pi. ix, figs. 3-6 ; text-figs. 29 and 30.) 

 Definition. Length 10 mm., width .75 mm. Somites 48. Setae 

 sigmoid ; laterals 3-4, ventrals 5-6. Head-pore small, opening half- 

 way between apex of prostomium and peristomium. Clitellum, dorsally 

 XI XIII, ventrally XII, XIII. A very large exterior copulatory 

 organ, almost as long as the diameter of the body. Brain anteriorly 



a. 



FIG. 29. Mesenchytrceus pedatus. 



slightly concave, posteriorly with straight margin, a trifle longer than 

 broad. Septal glands in IV, V and VI. Spermathecae each with two 

 club-shaped diverticles situated halfway up the organ. Sperm-funnels 

 two-thirds as long and broad as a somite. Sperm-ducts at least eight 

 times as long as the sperm -funnel. Sperm -ducts with an atrial chamber 

 before the penial pore. A ring of very large accessory glands open in 

 the immediate vicinity of the sperm-ducts. Dorsal vessel originates in 

 XIV. Nephridia with three somewhat indistinct lobes and a helix- 

 like posterior spur. Lymphocytes of two forms, oblong and round. 



