1909.] J. vStephenson : Aquatic animals from Tibet. 113 



There is nothing that can be called a stomach ; the intestine 

 is constricted at the septa, and bulges between the septa ; its 

 epithelium is columnar ; the tube is covered externally by round- 

 ish, slightly staining granular peritoneal cells, which may be so 

 numerous in places as to obliterate the body-cavit\\ 



Besides these peritoneal cells, there are body-cavity corpuscles 

 of circular shape, nucleated, very coarsely granular, the granules 

 appearing as highly refractive particles similar to those in some 

 species of Nais. 



The circulatory system is not sufficiently distinct for descrip- 

 tion ; the same may be said of the nephridia. The cerebral 

 ganglion is in segment i, not in the prostomium, and the nerve-cord 

 has the usual relations. 



The testes (fig. 4, te.) are in segment x, along with the sper- 

 mathecse ; the funnel (fig. 4, /.), also in x, is large, regular in 

 shape, sessile on the septum ; the vas deferens (fig. 4, v.d.), 

 whose walls are composed of a 1a5'er of somewhat cubical cells, 

 passes backwards in xi, presenting itself as a fairly stout tube, with 

 perhaps a gentle curve or two, but not coiled in an}' way ; a single 

 longitudinal section will sometimes cut nearly the whole length of 

 the tube ; probably in the extended condition of the animal it was 

 almost straight. It opens into the atrium at the inner end of the 

 latter. The atrium (figs. 3,4, atr.), in segment xi, is a somewhat 

 pear-shaped chamber , its broader end being internal ; it is prolonged 

 into the penis (figs. 3, 4, pen.), a short and somewhat inconspicuous 

 structure, whose chitinous sheath also is hardly to be made out 

 in mj'^ preparations. The prostate (figs. 3, 4, prst.) is a well- 

 marked mass of cells surrounding the inner end of the atrium on 

 all sides. 



The spermathecse (fig. 3, sp.) are in segment x, not extending 

 beyond this segment ; they may be bilobcd or not, or that of one 

 side may be bilobed, the other spherical. The lining epithelium 

 is much elongated near the external aperture, and some of these 

 elongated cells show clear spaces in their substance ; the same 

 condition of the epithelium is seen over the projection of the 

 wall into the cavity of the spermatheca where this organ is bilobed. 

 A hyaline non-staining material fills the spermathecae, aggregated 

 frequently into oval or elongated masses ( ? spermatophores). 



The ovaries (fig. 3, ovy.) are in segment xi, in close connection 

 with the vas deferens of each side. I have not identified the ovi- 

 ducts. 



The genital sacs (sperm-sac and ovisac) are large ; the male 

 products may extend forwards as a well-marked rounded mass into 

 segment ix. The combined sacs extend backwards through a 

 large number of segments, often to xviii, and even to xxv. The 

 male products are the more conspicuous and usually more bulky ; 

 the female products, ova with granular yolk, are usually posterior, 

 though they may have sperm-morulae behind as well as in front of 

 them. 



In a few specimens the ventral setae of segment xi are 



