ASCIDIA. 



289 



An incision will reveal at once that the body of the 

 mimal is enveloped in a thick test (or tunic) ^ out of which 

 the animal may be removed entire, like a bean 

 out of its pod. 1 he test is thick and of a 

 semi-transparent, gelatinous appearance. It 

 s produced chiefly by the layer of underlying ectoderm, 



Fig. 203. — DlAGRAMJVIATIC MEDIAN LONGITUDINAL SECTION 

 THROUGH AN AsCIDIAN. 



Internal 

 Features. 



Subneural I^ \ 

 Gland. 



Atriopore, 



Intestine 



Genital 

 Duct, 



Atrium. 



Dorsal 

 Blood-vessel.'" 



Buccal Cavity. 



■-~' Peripharyn- 

 geal Groove. 



Endostyle. 



Pharyngeal part 

 of Ventral 

 Vessel. 



Gonad. 



Stomach. Intestinal part of Ventral Vessel. 



The right half has been removed. 



and consists of a hyaline basis containing cellulose (a 



material mainly confined to the plant-kingdom), through 



which are scattered a number of cells. Below the 



M. 20 



