18 



ZOOLOGY 



SECT. 



running parallel with it, separated from it only by a narrow 

 groove, is another ridge of similar character : these are termed the 

 peripharyngcal ridges; the groove between them is the peri- 

 pharyngeal groove. Dorsally, i.e. opposite the endostyle, the 

 posterior peripharyngeal ridge passes into a median, much more 

 prominent, longitudinal ridge, the dorsal lamina (dors, lam.), which 



tent 



leal 



slont 



co.rd.visc 



FIG. 718. Ascidia, diagram of longitudinal section from the left side, the test and mantle 

 removed, an. anus ; atr. cav. atrial cavity; atr.siph. atrial siphon; br.car. branchio-cardiac 

 vessel; card, vise, cardio-visceral vessel; dors.v. dorsal vessel; gonod. gonoduct ; lit. heart; 

 hyp. neural gland ; tnant. mantle ; ne. (in. nerve-ganglion ; ces. oesophagus ; or. tsiph. oral 

 siphon ; ov. ovary ; rect. rectum ; stiy. stigmata ; stoin. stomach ; tent, tentacles ; text, test ; 

 tr. v. transverse vessel ; vent. r. ventral vessel ; vise. br. viscero-branchial vessel. (From 

 Herdman, after Perrier.) 



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

 opening of the oesophagus. 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 



