28 



EISEN 



very thick and swollen. Dorsal vessel rises in XVIII. Intestine 

 very gradually increases in size. Spermathecse strongly bent, at 

 the lower one-fourth furnished with two ovoid diverticles with 

 tliick epithelium. The ampulla very long and the apex swollen and 



Figs. 8 and 9. Mesencliytrceus setchelli, 



globular ; not connected with the intestine. Sperm-ducts about eight 

 times as long as the funnels, which latter are contracted at the middle. 

 Atrium with five atrial glands. Penial bulb with one set of glands, 

 confined to the interior of the bulb. Two long sperm -sacs extending 

 at least as far as XVIII. One ovisac. Nephridia with three large 

 lobes ; the anteseptal narrow and tubular. Lymphocytes ellipsoidal 

 and pointed. Color white. 



Locality. — Unalaska Island, August 10, 1899, Prof. W. A. Set- 

 chell. Eight specimens. 



Characteristics. — The most prominent character is the unusually 

 long spermathecae which extend through several somites, ending in VII 

 or VIII ; and which do not connect with the intestine. The ampulla 

 contains numerous spermatozoa and is so large that it fills the whole 

 available space in the somite. 



DETAILED DESCRIPTION (figS. 7) ^ ^^^ ^) • 



Sperinat/iecce. — To the above description of these organs only a 

 few points need be added. The part connecting the diverticles and the 

 ampulla bulges out in places and shows several smaller pouches, in 

 which also balls of spermatozoa were found. The presence of these 

 smaller pouches is however not constant, as they were not found in 

 two of the spermathecse. The wall of the spermatheca is thick in the 



