Pacific Thaliacea — Tokioka and Berner 
r.x. 
Fig. 7. Cyclosalpa strongylenteron Berner 1955, basal 
portion of left blind sac from left side. 
trally about two thirds of the way down the 
lower branch of the intestinal loop. Its distal 
end reaches far beyond the posterior margin 
of the loop. In the sinistral individuals the 
caecum is twisted counterclockwise around 
the alimentary tract, as in the case of the 
sinistral individuals of C. strongylenteron . In 
the dextral individuals the duct of the circum- 
intestinal gland (d.c.g.) opens into the intes- 
tine on the left side at the level of the anterio- 
basal portion of the caecum. In the sinistral 
individuals it opens into the base of the 
caecum itself. 
The testis (t.) is held completely within a 
posterior protuberance projecting from the 
posterior portion of the intestinal loop. It is 
considerably longer than in C. strongylenteron. 
The vas deferens runs across the right side of 
the intestine, crosses the duct of the circum- 
intestinal gland on the left side, and opens 
into the atrial cavity at a position far anterior 
to the anus. 
The right visceral muscle ( r.x .) runs down 
the right side of the intestinal loop to its pos- 
terior margin. The left visceral muscle {Lx.) 
projects deep into the posterior protuberance 
325 
with the testis. In the dextral individuals the 
caecum is superficially placed in the median 
plane and asymmetry can be found only in the 
arrangement of the vas deferens and the dif- 
ference in length of the visceral muscles. 
Such asymmetries are all of a primary nature. 
If the structure of the visceral regions of 
the aggregate forms of C. bakeri , C. strongylen- 
teron , and C. virgula are compared, we may be 
able to say to which C. strongylenteron is more 
closely related. On this basis it occupies an 
intermediate position between C. virgula , 
which has the small right caecum in both the 
dextral and sinistral individuals, and C. bakeri , 
in which the right caecum is lacking in both 
individuals. If, however, the musculature is 
phylogenetically more important than the 
structure of the visceral portion of the body, 
the above hypothesis is untenable. 
During the examination of C. bakeri two 
Fig. 8. Cylosalpa bakeri Ritrer 1905, visceral portion 
of dextral individual, from right side. 
