130 INVERTEBRATE ZOOLOGY 



In the mid- ventral line note the endostyle ; notice also that it 

 is a groove. Trace the endostyle forward to the base of the 

 siphon. At its anterior end the endostyle is continuous with a 

 ciliated ridge which encircles the anterior end of the pharynx 

 and is called the peripharyngeal ridge. This ridge is itself 

 continuous, on the dorsal side of the animal, i.e., on the side 

 opposite to the endostyle, with a ciliated longitudinal ridge called 

 the dorsal lamina, which passes along the mid-dorsal line to the 

 opening of the oesophagus at the posterior end of the pharynx. 

 Trace the peripharyngeal ridge and the dorsal lamina. 



These organs aid in the ingestion of the animal's food, which 

 consists of minute organisms and particles of organic matter. 

 The endostyle is a glandular and ciliated groove ; the gland- 

 cells secrete a viscid substance which catches the food particles ; 

 the cilia create a current which drives them towards the ante- 

 rior end. Here they meet a current created by the cilia of the 

 peripharyngeal ridges which takes them around the pharyngeal 

 wall to the dorsal lamina, along which they are driven poste- 

 riorly to the opening of the oesophagus. 



Between the two siphons note the ganglion and, beneath it, the 

 subneural gland. 



Exercise 5. Make a semidiagrammatic drawing showing the 

 structures which appear in connection with the pharyn- 

 geal wall. 



Exercise 6. Make a large diagram of Molgula and show the rela- 

 tive positions of the different organs ; label all. 



