lf>07.] NATURAL SCIENCES OF PHILADELPHIA. 401 



Ilaliolis uiulouljtedly possesses two renopericardial canals. I have 

 been able to demonstrate their presence, in the two species under dis- 

 cussion in this paper, both macroscopically and microscopically. They 

 may be seen readily in material from upwards of 0.5 cm. in length 

 (the smallest specimens I had) to that over 13 cm. long. 



For a study of these canals it will be well to commence with a con- 

 sideration of sections through specimens about 1.5 cm. long. The 

 first five figures should give one a fairly clear idea of the relations of 

 the renopericardial canals, pericardium, kidneys and gonoduct.^ 

 Neither of the canals is very long, and both may be regarded as funnel- 

 like outgrowths of the pericardium. The left canal (RE) is, however, 

 much the wider, and can be followed far more readily in material 

 properly prepared. 



The left renopericardial canal originates as a wide tube opening 

 into the pericardial cavity somewhat ventral to the point where the 

 rectum pierces the front wall of the same. Fig. 2 (RE') show^s the 

 mouth of this duct at the left lower corner of the pericardium, and that 

 of the right canal (RE) at the opposite corner. The former takes an 

 oblique course along the side and floor of the papillary sac (LK), into 

 which it opens between the papillae Throughout practicalh' its entire 

 extent it is lined with epithelial cells of moderate height apparently 

 totally devoid of cilia. 



The right renopericardial canal (RE) is a more slender duct, extend- 

 ing tow^ards the gonoduct (GO) from the inner, forward angle of the 

 pericardium. Its inner opening is relatively narrow and is situated 

 immediately beneath the right branchial sinus (fig. 2, S). At the right 

 of the pallial sinus (a branch of the branchial sinus) it may be seen 

 entering the side of the gonoduct (fig. 3). In fig. 5, which is six sec- 

 tions farther forwards, the gonoduct may be seen opening freely into 

 the cavity of the kidney at the point GO. In this connection it is to be 

 noted that the ventral wall of the gonoduct is very thin and extends 

 for some distance over the cavity of the kidney, unsupported by any- 

 thing except the body w^all above it. The right renopericardial canal 

 in specimens of this size (1.5 cm.) discharges into the left side of the 

 gonoduct, very close to the mouth of the latter — more so, in fact, than 

 is shown at GO in fig. A. 



An examination of large specimens of Haliotis by gross dissection 

 did not at first appear to confirm the results given above. Accord- 



^ The sections showii in figs. 1, 2, 3, 4, 5 of PI. XXX were made parallel with 

 the Une A-B of fig. A. 



