448 SUB-PHYLUM UROCHORDA OR TUNIC AT A. 



is usually complex, and forms the so-called dorsal tubercle, which 

 is very distinct on the wall of the pharynx. It lies at the point 

 where the two halves of the ciliated groove, or peripharyngeal band, 

 already described, converge dorsally to form the dorsal/lamina. In 

 Asddia the sub - neural organ is ventral to the bram, and partly 



Ph. 



A'. 



G.D. 



FIG. 241. Diagram of Ascidian After Herdman. 



The arrows indicate the two openings; the dark border the test. 

 Ph.) Pharynx, with gill-slits ; G., reproductive organs ; //., 

 heart, with blood vessels; G.JJ., genital ducts; R., rectum, 

 ending in cloacal chamber. Surrounding the pharynx the 

 peribranchial cavity is shown. 



glandular in character, and so it. is in many ; in some cases, however, 

 it is dorsal in position, and its glandular portion is reduced to nil. 

 It is probable that the sub-neural gland and its duct correspond to 

 the olfactory pit of Amphioxus t and perhaps to the hypophysis of 

 Vertebrates. 



