ENCHYTR^EID^E 



39 



part about one-half the diameter of the atrium. Atrial glands sur- 

 rounded by circular muscles at their entrance into the atrium ; all in 

 the same, or in almost the same plane, so that a single horizontal sec- 

 tion will cut them all at the same relative point. The narrow ducts 

 of the atrial glands do not seem to enter the lumen of the atrium and 

 penis, but continue down to the penial pore. Glands in the penial 

 bulb large, and rarely more than four visible in the same section. 



MESENCHYTR^US ORC^E sp. nov. 

 pi. xi, figs, i and 2; text-fig. 16. 



Definition. Length 6 mm., width .5 mm. Somites 33. Pros- 

 tomium large, round. Head-pore near apex. Intersegmental grooves 

 deep on ventral side. Clitellum XI-XIII ; clitellar cells unusually 

 large. Body entirely transparent. Setae : laterals, 4, 4, 4, 3, 4, 4, 4, 

 4, 4, 4, 3, 3, 3, 3, 4, 4, 3, 4, 4, 3,3,3; ventrals, 5, 6, 6, 7, 6, 6, 5, 



5 5i 5i 4 4 4 4> 5> 4> 4> 4 4? 5 3 4> 5> 4- Sexual papilla 

 small. Septal glands in IV to 

 VI. Brain longer than broad, 

 posteriorly truncate, anteriorly 

 deeply cleft. Dorsal vessel rises 

 in XV. Intestine with a few 

 chloragogen cells. Spermathecae 

 unusually enlarged, consisting of 

 an exceedingly long and slender 

 duct with two minute globular 

 diverticles at the center, and a 

 long and thick terminal ampulla extending as far back as X ; no con- 

 nection with the intestine. Funnels not above average size. Sperm- 

 ducts about twice as long as the funnels. Penial bulb narrow, with- 

 out any penial glands. A set of several large glands pierce the penial 

 bulb and enter the lower part of the sperm-duct just above the pore. 

 No accessory glands. Nephridia with several deep lobes. Lympho- 

 cytes disc-like, not large. Color white, no pigment. 



Locality. Orca, Alaska, June 25, 1899. Collected by Prof. 

 Trevor Kincaid. Two specimens found under rocks on the seashore, 

 above high tide. Also a few specimens from Yakutat, Alaska. 



Characteristics. Not only is the shape of the spermathecae char- 

 acteristic of the species, but the large atrial glands, which enter the 

 sperm-ducts at the pore inside the penial bulb, distinguish this species 

 from all others in the group with enlarged spermathecae. 



FlG> l6 . Mesenchytrvus ore*. 



