150 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY.. 



Just back of the brain a pair of branches from the main lateral 

 vessels pass obliquely upward to enter the cavity of the pro- 

 boscis sheath. These vessels lie on the ventro-lateral borders of the 

 rhynchocoel and project freely into its cavity. Near the middle of 

 the esophageal region they disappear, and probably join the dorsal 

 pair of lateral vessels, as in C. armandi. I was unable to demon- 

 strate any distinct communications, however, in the sections at my 

 command. 



Nejihridia. — The pair of nephridial canals makes its appearance 

 near the posterior end of the esophageal region, and extends a 

 short distance backward into the intestinal region. In the anterior 

 portions of the canals we find small, but complexly branching 

 tubules, which grow out into the ventral walls of the lateral blood 

 vessels, as described for other species of the genus. These tubules 

 are often almost completely surrounded by the blood, and the mass 

 of tubules constitutes the so-called nephridial gland (PI. 14, figs. 84, 

 85). This mass of tubules does not extend into the cavity of the 

 blood space nearly so far as in G. patagonica, but the tubules are 

 much more profusely branched than in C. armandi. The condition 

 in G. mutahilis is in many respects intermediate between the two 

 other species, and the general structure is closely similar to that 

 which Burger ('95) describes and figures in Garinina grata. The 

 minute tubules of the nephridial gland are lined with flattened 

 epithelium which lies in close contact with the similar epitheliuni of 

 the blood space. The complex of tubules extends backward just 

 about as far as the position of the external openings of the efferent 

 nephridial ducts — near the posterior end of the esophageal region. 

 Behind this point the nephridial canal changes its character entirely. 

 The tubule increases greatly in size (PI. 13, fig. 82; PL 14, figs. 83, 

 84), separates from the wall of the blood vessel, is no longer 

 branched or convoluted, and its epithelial lining changes from flat- 

 tened to columnar cells. These cells do not exhibit clearly marked 

 boundaries, but their positions are indicated by the regularly 

 arranged oval nuclei. Each cell commonly shows a very few short 

 cilia. The wide ciliated canal continues backward, with a few 

 irregular twists, into the anterior portion of the intestinal region. 

 Here it bends sharply on itself and passes forward again to the 

 region of the thickened internal circular muscles, where it enlarges 

 still more, and then bends obliquely upward, passes internal to the 



