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SHELL GALLERY. 
animal, which lives on a muddy bottom, in from five to twenty fathoms, 
resembles a conical sac fixed by the broader end, of grayish green 
colour and about 4 inches in height. At the narrower end are two 
orifices, one terminal — the branchial orifice or mouth, and the other 
a little lower — the atrial orifice : the former has eight lobes and the 
latter six. 
When the Ascidian is undistubed, the orifices are wide open, and 
currents enter by the branchial and leave by the atrial orifice. On 
the least alarm, the orifices close, jets of water being at the same 
time squirted out ; hence the popular name " Sea-squirts " given to 
these animals. 
The Ascidian is orientated as follows : hold the animal with the 
branchial orifice pointing forwards and the atrial upwards ; the 
branchial orifice will be anterior and the opposite end posterior ; the 
Diagrammatic section of Ascidia representing the three sacs, and the branchial 
sac as the pharynx or throat. 
a, branchial ; and b, atrial orifice ; c, tunic or test ; d, mantle ; e, branchial sac ; 
/, gullet ; g, stomach ; h, anal orifice ; i, dorsal lamina ; dotted line indicates 
the endostyle. 
atrial orifice will lie on the upper or dorsal aspect, the opposite 
aspect being lower or ventral, and the sides right and left. The 
aspects, in fact, correspond with those of a vertebrate animal. A 
