VENUS MERCENARIA LINNAEUS 219 



visceroparietal ganglion; yellowish Keber's or pericardial gland 

 in front of the pericard, wall of pericard; in the pericard the 

 ventricle of the heart with the rectum passing through it; thin, 

 transparent left auricle and arterial bulb in upper corner of 

 pericardial cavity; urinary bladder between posterior wall of 

 pericard and posterior retractor of the foot; under urinary 

 bladder the opaque, dotted kidney or glandular portion of the 

 organ of Bojanus; under the attachment line of the gill and 

 immediately behind the posterior wall of the pericard, the 

 minute left excretory opening of the kidney; in front of it, the 

 minute left genital opening. 



13. Take the injected specimen. Remove the left mantle 

 fold and the gills in the same manner as before. Remove Keber's 

 gland, left wall of pericard, left wall of urinary bladder and left 

 wall of cloacal chamber. With the aid of forceps and scalpel 

 remove carefully all muscles of the visceral complex and the 

 gonad. In removing the muscles take care never to pull at 

 more than one muscle bundle at a time and never to pull at a 

 deeper muscle until the bundles overlying it have been removed. 

 When the entire alimentary canal is exposed, it will appear as 

 a pink or red coiled tube. Make a full size drawing showing 

 outline of shell, edge of right fold of mantle, left retractor of 

 the siphon, siphons, anterior adductor, anterior retractor of the 

 foot, posterior adductor, posterior retractor of the foot, left 

 labial palps, dark, granulated liver; stomach extending in a curve 

 downward from upper edge of liver; coiled intestine, situated in 

 front of the stomach; thin rectum, situated behind the stomach 

 'and rising toward the edge of the pericard, where it passes 

 through the ventricle, runs thence dorsally to the posterior 

 artery over the posterior adductor and terminates in an anus 

 in the cloacal chamber. 



