54 



EISEN 



while other parts are attached to the lateral ducts leading to the 

 pharynx. 



Esophagus and tubular intestine throughout of very even thickness. 



Nephridia vary considerably as regards the form of the lobes. 

 Generally three lobes, and the whole nephridium is more or less 

 deltoid. 



Lymphocytes. Unusually large (fig. 15), ovoid or even circular. 

 In all the specimens sectioned, confined to the first thirteen somites. 

 The diameter of an average lymphocyte equals in thickness the epithe- 

 lium of the body-wall together with half the diameter of the transverse 

 muscular layer. They are strongly granular. 



MESENCHYTR^US FONTINALIS GRACILIS var. nov. 



Text-fig. 28. 



Definition. Length 5 mm., width .5 mm. Somites about 50. 

 Spermatheca with a pair of club-shaped diverticles situated about one- 

 third the distance from the intestine. In other respects similar to the 

 species. 



Locality. In mud of springs near Dinkey Creek, in the Sierra 

 Nevada, Fresno County, California. Altitude about 6000 feet. 



Characteristics. I can find no distinct 

 characteristics other than a greater slender- 

 ness of the spermatheca and a greater equality 

 of the two limbs. In the species the ampulla 

 between the intestine and the junction with 

 the diverticles is very short, much shorter than 

 the diverticle. In the variety, the ampulla 

 between the intestine and the junction of the 

 diverticles is about one and one-half times 

 as long as the diverticles, and the part be- 

 tween the pore and the junction of the di- 

 verticles is about two and one-half times 

 as long as the diverticles. The diverticles 

 also are longer in the variety than in the 

 species. These differences may be slight, 

 but the fact that they were found to be 

 constant in four specimens of the variety in 

 the six specimens of the species which I dis- 

 sected shows that they are of considerable importance and worthy 

 of being recorded. 



FIG. 28. Mesenchytrceus 

 fontinalis gracilis. 



