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PACIFIC SCIENCE, Vol. VIII, July, 1954 
first is interrupted middorsally, the remainder 
continuous, and four continuous ventral lip 
sphincters; independent muscle large and 
conspicuous. Ciliated groove: Similar to that 
of K. amhoinensis agg. Viscera: Similar to that 
of R. amhoinensis, except that the endostyle 
extends almost to the gut in K. picteti, whereas 
it extends only to the level of M V or less in 
R. amhoinensis. 
The solitary forms of R. picteti and R. am- 
hoinensis are rather similar to one another. 
Descriptions of them, however, vary con- 
siderably and should be reviewed, as there is 
much overlapping between descriptions and 
probable errors in them. All descriptions agree 
in regard to gut structure (except for those of 
Apstein [1906^, 1906/?] who evidently mis- 
takenly identified his specimens as 5. am- 
hoinensis). Ihle (1910) restudied these speci- 
mens and considered them to be 5. retracta. 
They had the characteristic T-shaped gut 
structure of R. picteti. 
In regard to muscle structure, however, 
there are a large number of contradictions. 
All past descriptions except Apstein’s (1904) 
of R. amhoinensis described M I-III as ring 
muscles. Apstein, however, in first describing 
the species, stated that the anterior muscles 
coursed almost to the endostyle and were 
thus interrupted. Ihle (I9IO) restudied these 
specimens that Apstein had described and 
stated for R. amhoinensis sol. that "die 3 vor- 
deren Korpermuskeln ebenso wie die Bogen- 
muskel ringformig sind." 
Sewell (1926), although not describing the 
condition, figured in R. amhoinensis sol. M 
I-IV as ring muscles; in most POFI spec- 
imens here examined, M I-IV are ring mus- 
cles; in some specimens, only M I-III are 
rings. 
Ritter (I9O6) emphasized the fact that in 
his specimen of Cyclosalpa retracta ( = R. pic- 
teti), M 2-10 were completely continuous 
ventrally, thus ring muscles. This has not been 
observed in any other specimen of the species. 
Apstein (1906^) described specimens, re- 
garded by him as S. amhoinensis, as possessing 
four "vollkommene Rundmuskeln," although 
in his earlier description (1904) of S. am- 
hoinensis all body muscles were considered to 
be ventrally interrupted. Ihle (1910) restudied 
these specimens that Apstein (1906^) had 
studied and identified them as S. retracta. He 
stated that with this species all body muscles 
were ventrally interrupted. Later, however, 
Ihle (1912) described the species S. retracta as 
follows: "Vordere Muskeln ringformig. . . . ” 
In specimens of R. picteti described by Ap- 
stein (1904), Ihle (1910), Sewell (1926), Ko- 
mai (1932), and Thompson (1948), all body 
muscles were described as ventrally inter- 
rupted. Apstein later (1906^, I906/?) made no 
mention of this condition even though he had 
done so in 1904. Ihle (1912), however, stated 
in regard to R. picteti, "Vordere Muskeln 
medio-ventral geschlossen." Also, Ihle (1935) 
characterized the genus Ritteriella as possess- 
ing 9-24 body muscles of which the " vorderen 
ringformig sind." 
Komai (1932) described a specimen of R. 
picteti in which all body muscles were ven- 
trally interrupted. In regard to Ritter’s (I906) 
description that C. retracta possessed nine ring 
muscles, Komai stated, "It is very doubtful 
whether one can put so much importance on 
that feature of the musculature in R. retracta, 
even if Ritter’s observation on this point is 
warranted.’’ I cannot agree with this state- 
ment, but rather believe that inconsistencies 
described have been the result of mistakes on 
the part of the observers. My conclusion is 
upheld by the POEI embryo, in which all 
body muscles and M C are ventrally inter- 
rupted. 
The blood-forming organ of R. amhoinensis 
has been described only as round or bean- 
shaped. In R. picteti (and S. retracta) it has 
usually been described as elongate, but Ihle 
(1910) described that of S. picteti as bean- 
shaped and that of S. retracta as variable in 
structure. Thus, this character perhaps is not 
important systematically. 
Descriptions of the stolon also vary con- 
siderably. In R. picteti it varies from a spiral 
