ASCIDIA. 445 
produced varies markedly in the different forms. In some 
forms the “test ”-cells make calcareous spicules. 
. In. ap. 
Fic. 240.—Dissection ot Ascidian.—After Herdman. 
Jn. ap., Inhalant aperture; 7., test, cut away below to show mus- 
cular layer, pharynx, etc.; Zx., endostyle or ventral groove 
of pharynx. Note removal of pharynx to show, on the other— 
the left—side, stomach (S7.), intestine (with fold seen at inci- 
sion), and reproductive organs (G.); H., opening of pharynx 
into cesophagus; G.D., genital duct; 4., anus; C/., cloacal 
chamber; £x. ap., exhalant aperture; Gz., lies above the 
ganglion, which is seen between the two apertures ; beneath it 
is the sub-neural gland and its duct. : 
Body wall and muscular system.—The body wall, mantle, 
or tunic, disclosed by peeling off the test, is a structure of 
considerable complexity. Its outer surface is covered by a 
