88 
THE ECHINODERMATA. & 86. 
In Holothuria tubulosa, they are cylindrical, pure white, and very nume- 
rous, being united in bundles which are attached to the digestive canal 
near the pharynx by short white pedicles.” 
In ‘Pentacta doliolum, there is usually only one of these organs,— a 
small, white, curved horn, which sends to the pharynx a very tortuous 
canal, which is widely removed from the excretory duct of the genital 
organs. 
“Phe whiteness of these organs in Holothurinae is due to a reticulated 
calcareous skeleton in their walls. 
The radial caeca of the Asteroidae cought probably to be regarded as 
hepatic organs. They are often quite developed, extending as a double 
canal from the stomach into each ray. Their walls have numerous small 
botryoidal vesicles, which secrete a yellow liquid. Usually each of these 
ten liver-like organs arises from the stomach by a proper canal; ® but in 
some, two of them connect with this organ by a single canal. 
With those Asteroidae which have an anus, there is another series of 
glandular appendages, the inter-radial caeca, which pass off from the rectum. 
‘Their function is not yet known. They contain a brownish liquid, in which, 
with Asteracanthion rubens, no uric acid has been found. In Astrogonium, 
Solaster, and Asteracanthion, these organs are branched, and only two in 
number. In Archaster, and Culcita, there are five; but in Culcita cori- 
acea, each of these is divided dichotomously into two other long botryoidal 
caeca, which, separated by a septum, are spread out between the rays. 
In Astropecten,‘’ which is without an anus, there are sometimes found two 
short, analogous caeca, which open into the base of the stomach by a com- 
mon orifice. 
are entirely absent. 
But in Lwtdia, which is also without an anus, these organs 
In the other Hchinoderms, which are entirely without these glandular 
appendages, the walls of the alimentary canal probably secrete the fluid 
requisite for digestion, and thus supply also the want of the hepatic 
organ. 
1 It has already been shown that the cylindrical 
vesicles of Holothuria taken by Cuvier and other 
naturalists for salivary organs do not communicate 
with the digestive canal, but rather with the tenta- 
cles. The white appendages of Holothuria tubu- 
losa were first described as testicles by Delle 
Chiaje (Memor. &c. I. p. 97, Tav. VIII. fig. 1. 0.), 
and Tiedemann (loc. cit. p. 29, Taf. IL. fig. 6, 
p.) assigned to them the same function. It is cer- 
tain that they have no testicular character, although 
I cannot affirm that they are salivary organs. 
They shave been figured, in Holothuria atra, by 
Jaeger in his dissertation: De. Holothuriis, Tab. 
III. fig. 2, e. e. 
2 This calcareous tissue has been observed by 
Jaeger (loc. cit. p. 88, Tab. III. fig. 7), by Wag- 
ner (Froriep’s neve Not. No. 249, 1839, p. 99), 
and by Krohn (Ibid. No. 356, 1841,’p. 53). This 
last okseryer, who affirms that these organs are in 
connectio.. with the great circulatory vessel sur- 
rounding the digestive canal, compares them to the 
stony canal of the Asteroidae. 
3In Astropecten aurantiacus, according to 
Tiedemann (loc. cit. Taf. VII. or, Wagner, Icon. 
zoot. Tab. XXXII. fig. 1). It is the same, also, in 
Archaster, Culcita, and Luidia ; see Muller and 
Troschel, loc. cit. p. 182, Taf, XI. fig. 2; Taf. 
XIU. fig. 1. 
4 Asteracanthion ; see Konrad, De Asteria- 
rum fabrica, fig. 1; and Muller and Troschel, 
loc. cit. Taf. XI. fig. 2. 
5 See Miller and Troschel, loc. cit. p. 182, Taf. 
XI. fig. 1 (Asteracanthion rubens); an entire 
group of these rectal coeca of Asteracanthion 
glacialis, has been figured by Konrad, loc. cit. 
g.1,d. 
§ Muller and Troschel, loc. cit. p. 132, Taf. XI. 
fig. 2, Taf. XII. fig. 1. 
7 Tiedemann, loc. cit. Taf. VII. 
8 Miller and Troschel, loc. cit. p. 182. 
9 According to Valentin’s figure of the inti- 
mate structure of the digestive membranes of Echi- 
nus, they are lined with hepatic epithelium, like 
‘that of the Lumbricinae, and that of the Polyps, 
already mentioned (Monogr. &c. Pl. VII. fig. 126, 
181, 183). 
