426 SUB- PHYLUM UROCHORDA OR TUNIC AT A. 



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

 structure of considerable complexity. At its upper end it is 



In. ap. 



FIG. 209. Dissection of Ascidian. After Herdman. 



In. ap., 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.)\ If., opening of pharynx 

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

 chamber; Ex. ap., exhalant aperture; Gti,, lies above the 

 ganglion, which is seen between the two apertures ; beneath it 

 is the sub-neural gland and its duct. 



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

 exception of the openings at their tips, it completely invests 

 the body. Its outer surface is covered by a single layer of 



