EXERCISE IV. 
THE SEA-SQUIRT (Boltenia australis ). 
Sub-kingdom—TuNniIcata. Class —ASCIDIOIDA. 
1. Cut off the peduncle about a third of an inch from the 
body, and lay the animal on the cork with the 
peduncle from you and the two lateral openings on 
the right side. Fasten down with two pins, one 
through the peduncle, the other through the end 
next to you. Make a transverse incision through 
one of the ribs of the tunic close to the peduncle 
and cut out a longitudinal strip of the thick tunic. 
Cut away, piece by piece, other portions of the tunic 
until the whole of the upper half has been removed, 
taking care not to cut on the right side lower down 
than the bases of the two projections on which the 
openings are situated. 
2. Cover with water. Notice the muscular “second tunic” 
—the so-called mantle, probably homologous with 
the sub-cutaneous muscular layer in annelida. The 
muscular bands are more or less transverse, becoming 
circular round the openings, thus forming sphincters. 
It passes into a central cavity in the peduncle. 
The mantle is covered externally by a thin trans 
parent membrane, which can be easily removed. This 
is the eutis, which secretes the tunic. 
3. Open the mantle by an incision carried round both 
sides and the end nearest to you; carefully detach it 
from the viscera, and lay it back over the peduncle. 
