108 INVERTEBRATE ZOOLOGY 



white nerve collar, the dorsal portion of which is the brain. If, 

 however, the animal died in a retracted condition the pharynx 

 may have slipped back through the nerve collar, which would 

 then encircle the forward end of that organ. Note the two 

 white, leaf-like salivary glands which lie close against the wall 

 of the stomach, and trace their ducts forward to the pharynx. 

 Lying above and across the ossophagus is the white cylindrical 

 penis, which will be seen to extend from the genital pore at 

 the right of the mouth and to bend sharply on itself. The 

 bend of the penis is connected by a long retractor, muscle to 

 the dorsal body-wall. Find it ; cut it and pin the penis on the 

 animal's right. Note the broad, glistening retractor muscle 

 connecting the pharynx with the ventral, posterior body-wall. 

 Notice its shape ; with strong forceps pull it loose from the 

 pharynx and entirely remove it. Also beneath it, note the still 

 larger retractor muscle running from the forward end of the 

 head back to the same locality. What is the function of these 

 different retractors ? The dark-colored sheaths and the retractor 

 muscles of the tentacles will also be seen ; trace these muscles 

 to their origin. Find the nerve which passes from the brain 

 into each tentacle. 



Separating the delicate filaments connecting the stomach with 

 the surrounding organs, and pushing it and the oasophagus to 

 the animal's left, find the large nervous mass which forms the 

 ventral portion of the nerve collar, and the nerves radiating 

 from it. It is an agglomeration of ganglia, being made up 

 principally of the pedal and the visceral ganglia. Press the repro- 

 ductive organs to the animal's right and pin them down. The 

 receptaculum seminis, a small spherical body the size of a shot, at 

 the end of a long tube, will be found in a bend of the intestine, 

 from which it must be separated. 



We turn now to the other end of the intestine. Trace the 

 rectum from the anus to the point where it is surrounded by 

 the liver and carefully dissect away the integument which covers 



