316 
PACIFIC SCIENCE, Vol. VIII, July, 1954 
AGGREGATE FORM: Seven specimens exam- 
ined with length range of 33-71 mm. (Fig. 
23). Test' Asymmetric, thick and firm except 
on lips and cloacal siphon; dorsal depression 
broad, extending from dorsal lip to above 
cloacal siphon; a broad dorsal limiting eleva- 
tion on each side; transverse groove at base 
of dorsal lip; other transverse grooves and 
folds occuring incidentally over test; lateral 
depression shallow or forming deep grooves; 
ventral surface greatly thickened, especially 
over chin and gut swelling; large spines with 
a rather constant arrangement over test ac- 
cording to animal’s location on the stolon; 
three longitudinal rows on dorsolateral eleva- 
tion of one side, one row extending postero- 
ventrally onto gut swelling; gut swelling with 
few spines on postero ventral region; on op- 
posite side of test, two longitudinal rows on 
dorsolateral elevation continuing anteroven- 
trally with a group of spines crossing lateral 
depression, extending onto chin; several spines 
present on posterodorsal and posteroventral 
regions of gut swelling; one group of spines 
extending transversely over dorsaj lip; scat- 
tered spines in middorsal depression. Number 
of attachment organs varies, asymmetric in 
arrangement. Muscles: Five body muscles, in- 
terrupted dorsally and ventrally, extending 
only to sides of body; weakly developed, 
being interrupted in various places; M I-III 
converging dorsally but not touching; M V 
bifurcates; prominent blood vessels accom- 
panying muscles. Ciliated groove: A large open 
loop. Viscera: Gut compact, in state E (Ihle 
and Ihle-Landenberg, 1933); endostyle nar- 
row, sinuous; three or four embryos attached 
dorsally between M IV and V (Thompson, 
1948). 
Except for Helicosalpa komaii (230 mm.), 
the solitary form of this species is the largest 
of the salps (up to 226 mm. according to 
Traustedt, 1885). It was well figured (solitary 
form) by Traustedt (1885) and Stiasny (1926). 
Fig. 23. Thetys vagina, aggregate form, a. Whole animal, dorsal aspect; b, another specimen, lateral aspect 
(length, 38 mm.); c, same specimen as a, ventral aspect of test; d, schematic cross section of test at level of M III. 
