236 CHORDATA 



atrial cavity open the intestine and the gonoducts, and also 

 the numerous stigmata of the pharynx. Ventrally the 

 pharynx is fused with the mantle in the region of the endo- 

 style. 



1. On each side of the upper part of the pharynx six 

 longitudinal pharyngeal folds will be seen. 



2. The endostyle is a ciliated groove along the midventral 

 wall of the pharynx. In a very fresh specimen, cut out a 

 large piece of the ventral and left lateral wall of the pharynx, 

 preferably near the siphon, mount it inside up in sea water 

 and examine with a microscope. Note the structure of the 

 endostyle. At some distance from the endostyle, on each side 

 of it, note the meshwork of blood vessels, and the curved 

 openings or stigmata lined with cilia. Of what use are the 

 cilia? 



3. Anteriorly the endostyle is continuous with the peri- 

 pharyngeal ciliated bands, which encircle the oral end of the 

 pharynx. From the point where they unite dorsally the 

 dorsal lamina extends backward along the mid-dorsal line of 

 the pharynx. At its posterior end will be seen the small 

 opening into the esophagus. 



Do you understand how the animal captures its food and 

 how the endostyle, peripharyngeal bands, and dorsal lamina 

 are used? 



4. In front of the anterior end of the dorsal lamina note 

 the small, volute-shaped dorsal tubercle. This is the ex- 

 tremity of the hypophysis, a tuhe connecting the subneural 

 gland with the oral cavity. 



5. A ring of oral tentacles will be seen in the mouth, an- 

 terior to the peripharyngeal bands. Of what use are ten- 

 tacles in the mouth? How many tentacles are there? 



6. The very short esophagus opens into the stomach, 

 which will be recognized by the brown digestive glands that 

 cover it. From the stomach the intestine forms a loop on 

 the left side, and is easily traced to the anus, which opens 

 dorsal to the pharynx in the atrial chamber. A longitudinal 



