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ring of tentacles around its posterior border ; these tentacles 

 form the sieve-like entrance to the large pharynx, which 

 extends to the posterior end of the body. The rest of the 

 gut is on the left side of the pharynx, and is largely embedded 

 in the mantle ; and it consists of a short oesophagus, a 

 pyriform stomach, and a looped intestine ending in a dorsal 

 anus which opens into the atrial outlet. 



The pharynx has walls with numerous transverse rows 

 of ciliated gill-slits ; and along its inner ventral surface 

 there is a ciliated groove with glandular cells, the endostyle, 

 opposite which is a ciliated fold along the inner dorsal 

 surface, the dorsal lamina, extending to the oesophagus. 

 Both are connected with a ciliated circular peripharyngeal 

 groove below the tentacles round the entrance to the 

 pharynx. The cilia of the endostyle force the slime (secreted 

 by its gland cells) forward into the peripharyngeal groove ; 

 and the slime is moved on round that groove and thence 

 down the dorsal lamina. The water-borne food particles 

 and organisms are caught in the moving slime, and aro 

 in that way conveyed into the oesophagus. Water is 

 drawn in at the mouth into the pharynx or branchial sac, 

 which, having highly vascular walls for the aeration of the 

 blood, also acts as a respiratory organ. The current is 

 kept going by the action of the cilia on the gill-slits, through 

 which the water passes into the atrium, the large space 

 between the pharynx and the body wall. The water 

 passes out through the atrial aperture. 



The only remaining part of the nervous system is the 

 trunk ganglion, situated between the mouth and the atrial 

 opening. The ventral heart is a simple sac situated below 

 the ventral end of the stomach ;. it has a reversing action, 

 which causes a periodic change in the direction of the 

 blood-flow ; it is placed within the pericardium, which, 

 along with a small associated space, represents the coelome 

 or body cavity. 



The hermaphrodite reproductive organs (an ovary sur- 

 rounded by a testis) are situated in the loop of the intestine ; 

 and the ducts (oviduct and vas deferens) together lead into 

 the atrium, and open near the anus. The gonads mature 

 at different times (i.e., dichogamy. See page 12, Part I.). 



