XII 



PHYLUM CHORDATA 



3*7 



this structure, consisting of the two ventral longitudinal folds with the 

 groove between them, the term endostyle is applied. The cells covering 



leal 



tr.tr 



mant 



Venl.V 



br.car 



■vLsc.br 



card.i/Lsc 



Fig. 199. — Ascidia, diagram of longitudinal section from the left-hand side, the test 

 and mantle removed, atr. cav, atrial cavity; atr. siph, atrial siphon; br. car, 

 branchio-cardiac vessel; card, vise, cardio-visceral vessel; gonad, gonoduct; 

 ht y heart; hyp, hypophysis ; mant, mantle ; n.gn, nerve-ganglion ; oss, oesopha- 

 gus ; 07\ ovary ; red, rectum ; stig, stigmata ; stom, stomach; tent, tentacles; 

 test, testis; tr. v, transverse vessel; vent, v, ventral vessel; vise, br, viscero- 

 branchial vessel. (After Herdman.) 



the endostyle are large cells of two kinds — ciliated cells and gland cells, 

 — the former beset at their free ends with cilia, the action of which is 



