398 



UROCHORDA OR TUNIC ATA. 



Body-wall and muscular system. — ■ The body-wall, 

 mantle, or tunic, disclosed by peeling off the test, is a 



Fig. 173. — Dissection of Ascidian.— After Herdrnan. 



In. afi., Inhalant aperture ; T., test, cut away below to show mus- 

 cular layer, pharynx, etc. ; En., endostyle or ventral groove 

 of pharynx. Note removal of pharynx to show, on the other — 

 the left — side, stomach (St.), intestine (with fold seen at inci- 

 sion), and reproductive organs (G.) ; H., opening of pharynx 

 into oesophagus; G.D., genital duct; A., anus; CI., cloacal 

 chamber; Ex. af., exhalant aperture; Gn., lies above the 

 ganglion, which is seen between the two apertures ; beneath 

 it is the sub-neural gland and its duct. 



structure of considerable complexity. At its upper end it is 

 more or less drawn out into the two siphons, and, with the 

 exception of the openings at their tips, it completely invests 



