5O EISEN 



Locality. West Fork of Feather River and Goose Lake, northern 

 Modoc County, northern California, Dr. R. C. McGregor. Several 

 specimens. 



Characteristics. This variety differs from the species in the shape 

 of the spermatheca, and in the absence of pigment granules in the 

 body-wall. There is also a difference in the form of the sperm-funnel 

 and in the shape of the prostates, as will be shown below. 



DETAILED DESCRIPTION. 



I will only dwell upon points in which the variety differs from the 

 species. 



Body-wall. There are no pigment granules in any of the somites. 

 The specimens are white, those of the species being anteriorly strongly 

 tawny. 



Spermatheca. The diverticles of the spermatheca (fig. 24, a) are 

 much smaller than in the species, as a comparison of the figures will 

 show. In the species the diverticles are about one-third as long as the 

 whole spermatheca, while in the variety they are two-elevenths as long. 



Spermiducal apparatus . The atrial glands enter the atrium nearer 

 the penial chamber than in the species. There is also a difference in 

 the form of the glands, which in the variety are more oblong. In the 

 species they are more rounded. 



MESENCHYTR^US EASTWOODI sp. nov. 

 pi. I, fig. 12 ; pi. vi, fig. 3; text-fig. 25. 



Definition. Length 6 to 8 mm., width .6 mm. Somites 65. 

 Seta? : ventrals, 6, 6, 6, 5, 6, 6, 5, 5, 6, 5, 6 (XII), 4 (XIII), 4, 4; 

 laterals, 2, 2, 3, 3, 3, 3, 3, 3, 2, 2 (XII), 2 (XIII), 2, 2, 3, 3, 3, 2. 

 The most lateral setae in the ventral fascicles and the most ventral in 

 the lateral fascicles are smaller. Head-pore on the upper side of pro- 

 stomium, which is short, blunt, and rounded. Brain anteriorly deeply 

 emarginated, posteriorly straight ; longer than wide. Dorsal vessel rises 

 posterior to XV. Intestine with small flat chloragogen cells. Sper- 

 mathecae with a pair of cylindrical diverticles at the center, each diverti- 

 cle being a little shorter than half the spermatheca. Sperm-ducts about 

 eight times as long as the funnels. Funnels small, almost globular, with 

 twisted basal part. A comparatively narrow atrium exterior to the 

 penial bulb. Two long and irregular atrial glands open in the atrium. 

 Six or eight penial glands inside the bulb open at the penial apex. 

 Two pairs of sperm-sacs well developed. Lymphocytes oval, with 

 pointed ends, about one-fifth as long as the narrow diameter of the brain. 



