A. E. Yerr'dl — North American Cephalopoch. 3;i7 



is divided into two chambers by a median, thin, membranous par- 

 tition. 



The branchial chamber is separated from tlie visceral cavity by a 

 thin, translucent membrane, through which there are two cii-ciilar 

 openings (w), one a short distance in advance of the base of each gill ; 

 tlirough these the secretions of the urinary organs (r, r') are doubtless 

 discharged. Internally the visceral cavity is divided into several com- 

 partments by folds of thin membrane. The largest of these chambers 

 contains the stomach and its coecal lobe {S, S'). When tlie branchial 

 cavity is opened on the ventral side, as in PI. XL, fig.l, and the 

 thin membranes covering the viscera are removed, the renal organs 

 (r, r') are seen, as large and conspicuous organs, especially if the 

 venous system has been injected with a colored fluid. Tliese organs 

 are situated below, above, and in front of the heart, but two pyri- 

 form glands (r', r'), which are firmer and have a more compact struc- 

 ture than the rest, extend along the posterior venae-cavte. The an- 

 terior ones, in front of the heart, consist of a number of groups or clus- 

 ters of lobulated glandular follicles, developed upon the posterior 

 part of the anterior vena-cava and upon its saccular divisions, on the 

 hepatic veins, on the intestinal veins, and on other large veins going 

 toward the branchial auricles {au). Two of the larger divisions (r, r), 

 which are elongated, and lie below and across the heart and large 

 efferent vessels {bo) returning from the gills, arise as direct forks of 

 the vena-cava, which divides just in front of the origin of the intestine ; 

 these forks pass each side of the intestine and each gives oflf a dorsal 

 branch, which runs up along the basal part of the intestine and joins 

 the large saccular renal vessels that lie above the heart, on each side. 

 These dorsal, renal vessels extend backward beyond the heart ; they 

 receive the blood from the gastric veins posteriorly and from two 

 hepatic veins anteriorly ; laterally, they communicate directly with 

 the branchial auricles. 



The ventricular heart {H) is a rather large, muscular, median, some- 

 what unsymmetrical organ, varying in shape according to the state 

 of contraction. Usually it is more or less obliquely four-cornered, 

 with the right side largest and the posterior end more or less conical. 

 From the posterior end arises a large artery, the posterior aorta, 

 which gives oiF, close to its origin, two small arteries ; one of these 

 is median, and goes forward to the ink-sac, passing below the heart ; 

 two branches, close to its origin, go to the renal organs (r, r), on each 

 side; the other, arising laterally, goes to the prostate gland and other 

 organs connected with it, (PI. XL, fig. 2, />o). A little farther back 



