XII 



PHYLUM CHORDATA 



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

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



Unt 



Ual 



br.car 



fLSc.br 



slom, 



ca.rtl.viao 



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

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

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

 hi, heart; hyp, hypophysis ; mant, mantle; n.gn, nerve-ganglion; aes. cesopha- 

 gus ; ov, ovary: rect, rectum ; stig, stigmata; stont, 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 



