18 



ZOOLOGY 



running parallel with it, separated froni it only by a nanw 

 PTOove is another ridge of similar character : these are termed the 

 pcrl'phn-migcal ridges ; the groove between them is the ven- 

 fharyngcal groove: Dorsally, i.<: opposite the endostyle, the 

 posterior peripharyngeal ridge passes into a median niucdi more 

 prominent, longitudinal ridge, t\^& dorsallamina {dors, htm.), xvhich 



runs along the middle of the dorsal surface of the pharynx to the 

 opening of the cesophagus. In the living animal the lamina is 

 capable of being bent to one side in such a way as to form a deep 

 groove. The mucus secreted by the gland-cells of the endostyle 

 forms viscid threads which entangle food-particles (microscopic 

 organisms of various kinds); the cilia of its ciliated cells drive 



