Pacific Salpidae — YoUNT 
311 
(Apstein, 1906^, identified by him as S. am- 
boinensis) to an elongate vermiform structure 
with a slight bend; in K. amhoinensis it forms 
a wide sickle-shaped curve or is straight but 
may be slightly spiralled; thus, this organ also 
is perhaps not important systematically. 
It is obvious from the literature that there 
has been a considerable amount of confusion 
in identifying the two solitary forms. Also 
obvious, both from the literature and POFI 
specimens, is the fact that these forms have a 
wide range of variability, perhaps more than 
any other salp, especially in muscle number 
and condition. I believe, however, that the 
differences in gut structure and in interrup- 
tions of the body muscles are important and 
valid* differences. They are applicable to all 
POFI specimens, at any rate, except for the 
gut of the embryo of K. picteti. 
The gregarious form of R. amhoinensis has 
long been known (but that of R. picteti has 
only recently been described) by Berner 
(1954). Apstein (1904) first described the 
aggregate form of R. amhoinensis rather in- 
adequately, not describing the mouth or 
cloacal muscles. His figure does not permit 
accurate identification. Ihle (1910) studied 
this form next, describing both older chain 
forms and very young stolonic individuals. 
His descriptions are thorough and adequate 
for identification of R. amhoinensis agg. He 
described and figured three sphincters in each 
lip (Taf. I, fig. 10) of the chain specimens. 
All these sphincters were described as un- 
interrupted. Metcalf (1918) based his de- 
scription completely on that of Ihle (1910). 
He reproduced Ihle’s figure 10 among others, 
thus showed three sphincters in each lip; but 
he described it as follows: ”The oral muscles 
(Fig. 31) include a retractor and, in the upper 
and lower lips, two sphincters each. . . .” It 
may be thought that he considered the finer 
sphincters as only branches of one main 
sphincter, thus two in each lip, but in his 
other descriptions, each mouth muscle, no 
matter how small, was distinguished by a 
name and number. Therefore, he obviously 
misread Ihle (1910) and, although reproduc- 
ing Ihle’s figure correctly, he described the 
animal incorrectly. Thompson (1948) based 
most of his descriptions on those of Metcalf 
(1918) and repeated Metcalf’s error in the 
description of R. amhoinensis agg. Thompson’s 
figure shows only two sphincters in each lip, 
but as the figure is of the whole animal, de- 
tails were probably overlooked in the mouth 
musculature. He also reproduced Ihle’s figures 
(1910) but described the animal inaccurately, 
although Ihle had clearly labeled the three 
sphincters in each lip. 
Berner (1954) identified the aggregate form 
of R. picteti by the embryo held within them 
and distinguished the form chiefly by the 
following features: (1) the body muscles are 
composed of more fibers and are thus wierd, 
and (2) the lip muscles of R. picteti include 
three sphincters in each lip, whereas there are 
only two in R. amhoinensis. He apparently 
carried on the error of Metcalf and Thompson 
in his statement that the aggregate form of 
R. amhoinensis has two sphincters in each lip. 
I have found two specimens of the aggre- 
gate form of R. picteti in the POFI collections 
as well as six specimens of R. amhoinensis and 
thus have been able to make a thorough 
comparison. 
The major differences noted are: 
1. possesses three dorsal lip sphinc- 
ters (Ai, Bi, B2) and four ventral lip sphincters 
(ai, a2, as, bi), one of which, a2, remains hid- 
den beneath the more conspicuous as; in R. 
amhoinensis there are three dorsal lip sphincters, 
one of which, Bi, is very small and thus in- 
conspicuous, and the ventral lip also contains 
three. 
2. As Berner (1954) showed, in R. picteti 
upper-lip sphincter 1 (Ai) is interrupted mid- 
dorsally, whereas in R. amhoinensis it is con- 
tinuous. 
3. The gut swelling of R. picteti is con- 
spicuous and almost completely independent 
of the remainder of the body (as described in 
some specimens by Ihle, I9IO; thus, if this 
