^8 THE ECHINODERMATA. ^ 86. 



In Hohthuria tuhulosa, 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 Fentacta doliohim, 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 hav.e 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 oif from the rectum. 

 Their function is not yet known. They contain a brownish liquid, in which, 

 with Aster acanihion ruhens, no uric acid has been found. In Astrogonium, 

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

 number.® In Archaster, and Culcita, there are five ; but in Cidcita 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 Astrojjecten,'''' 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 



1 It has already been shown that the cyliiidrical Tiedemann (loc. cit. Taf. VII. or, Wasner, Icon, 



vesicles of Hotoihuria taken by Citvier and other zoot. Tab. XXXIl. tig. 1). It is the same, also, in 



naturalists for salivary orj,'an3 do not communicate Archaster, Culcita, and Luidia ; see MuUer and 



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



<;les. The white appendages of Holothuria tuba- XII. fig. 1. 



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



Chiaje (.Memor. &c. I. p. 97,Tav. Vlll. fig. 1. c), rum fabrica, fig. 1 ; and Müller and Trosckel, 



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



p.) as-i-iM ,1 t i tliem the same function. It is cer- S See Müller and Troschel, loc. cit. p. 132, Taf. 



tain that Uir\ li;ive no testicular character, although XI. fig. 1 {Asteracanthion rubetis); an entire 



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



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



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



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



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



Jaeger (U,c. cit. p. 38, Tab. III. fig. 7), by fVag- ? Tiedemann, loc. cit. Taf. Vn. 



ner(Froriep\i neue Not. No. 249, 1839, p. 99), 8 Müller and Troschel, loc. cit. p. 132. 



and by ATro/m (Ibid. No. .356, 1841, p. 53). This 9 According to Valentin's figure of the inti- 



last oJ-server, who uflirms that these organs are in mate structure of the digestive membranes of Kchi- 



connectio.; with the great circulatory vessel sur- nns, they are lined with hepatic epithelium, lilco 



rounding the digestive canal, compares them to the that of the Lunibricinae, and tliat of the I'olyjis, 



stony canal of the Asteroidae. already mentioned (Monogr. &c. PI. VII. fig- 126, 



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



