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Fig. 31.—Single zooid of P. giganteum, with the test 
process on which the branchial orifice opens. 
Ascidiozooids—Fig. 31. Varying in length, depending on 
the length of the branchial siphon, but branchial sae in full 
erown zooids quite constantly about 3 mm.; length, including 
both siphons, 5 mm. to 6 mm. The large branchial sac much com- 
pressed, varying in form from approximately square with some- 
what rounded angles, to pronouncedly elongate. Branchial ori- 
fice in some zooids but slightly above the general level of the test 
surface; while in others it is high up on the above described 
oblique planes of the test processes. In these latter zooids the 
branchial siphon is long and narrow. Branchial tentacles 
close within the branchial orifice, however long this may be; 
tentacles few and short, a single one on the ventral side distinctly 
longex. 
Largest number of branchial stigmata seen, thirty-two, on 
each side of sae; maximum number of internal branchial vessels, 
fifteen. Dorsal languets, six to eight. Intestinal tract project- 
ing but little behind branchial sac; esophageal mouth at the 
dorso-posterior angle of the branchial sac, esophagus nearly as 
long as the loop of the intestine proper; stomach globular or egg- 
