88 THE ECHINODERMATA. <§> 86. 



In Holothuria tuhidosa, they are cylindrical, pure white, and very nume- 

 rous, being united in bundles which arc 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. 



The whiteness of these organs in Holothurinae is due to a reticulated 

 calcareous skeleton in their walls. ^-' 



The radial caeca of the Asteroidae ought 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 Aster acanthion rubens^ no uric acid has been found. In Astros:onium, 

 Solaster, and Asteracantkmn, these organs are branched, and only two in 

 number. '^^ In Archaster, and Cuicita, 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. But in Luidia, which is also without an anus, these organs 

 are entirely absent.'*' » 



In the other Echinoderms, 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 Tiedemann (loc. cit. Taf. VII. or, Wagner, Icon, 

 vesicles of Holothuria taken by Cuvier and otlier zoot. Tab. XXXII. fig. 1). It is the same, also, in 

 naturalists for salivary organs do not communicate Archaster, Cuicita, and Luidia ; see Muller and 

 with the digestive canal, but rather with the tenta- Troschel, loc. cit. p. 132, Taf. XI. fig. 2 ; Taf. 

 cles. The white appendages of Holothuria tubu- XII. fig. 1. 



losa were first described as testicles by Delle 4 Aster acanthion ; see Konrad, De Asteria- 



Chiaje (Memor. &c. I. p. 97,Tav. VIII. fig. 1. o.), rum fabrica, fig. 1 ; and Muller and Troschel, 



and Tiedemann (loc. cit. p. 29, Taf. II. fig. 6, loc. cit. Taf. XI. fig. 2. 



p.) assigned to them the same function. It is cer- 5 See Muller and Troschel, loc. cit. p. 132, Taf. 



taiu that they have no testicular character, although XI. fig. 1 (Asteracanthion rubens); an entire 



I cannot affirm that they are salivary organs, group of these rectal coeca of Asteracanthion 



They have been figured, m Holothuria atra, by glacialis, has been figured by Konrad, loc. cit. 



Jaeger in his dissertation : De. Holothuriis, Tab. fig. 1, d. 



III. fig. 2, e. e. « Muller and Troschel, loc. cit. p. 132, Taf. XI. 



2 This calcareous tissue has been observed by fig. 2, Taf. XII. fig. 1. 



Jaeger (loc. cit. p. 38, Tab. III. fig. 7), by Wag- 1 Tiedemann, loc. cit. Taf. Vn. 



ne/ (Froriep's neue Not. No. 249, 1839, p. 99), S Muller and Troschel, loc. cit. p. 132. 



and by Krohn (Ibid. No. 356, 1841, p. 63). This 9 According to Falentin''s figure of the inti- 



last observer, who affirms that these organs are in mate structure of the digestive membranes of Echi- 



connection with the great circulatory vessel sur- nus, they are lined with hepatic epithelium, lilie 



rounding the digestive canal, compares them to the that of the Lumbricinae, and that of the Polyps, 



Btony canal of the Asteroidae. already mentioned (Monogr. &c. PL VII. fig. 126, 



3 In Astropecten aurantiacus, according to 131, 133). 



