$ 86. THE ECHINODERMATA. 87 
spirally, consists of a spongy substance, from which projects a lamina like 
the lamina spiralis of the conch of a snail shell. 
In Spatangus, the toothless mouth opens into a delicate esophagus 
which passes insensibly into a long tube of nearly the same size. This 
last makes two convolutions in its course, and sends off at about its anterior 
fourth a very long caecum. The digestive canal, situated between the origin 
of this caecum and the esophagus, is of a dark color and has transverse 
plicae, while the remaining portion below is smooth and of an orange hue. 
In the Clypeastridae, the numerous spiral turns of this canal are sup- 
ported by many calcareous lamin situated upon the interior of the shell. 
In many species of Clypeaster, this canal has at its commencement, 
transverse folds, and further on numerous lateral caeca, which are sepa- 
rated from each other by laminze like those just described.© 
‘In the Echinidae the pharyngx has very thick muscular walls, and is 
surrounded by masticatory organs. Upon it succeeds a proper cesophagus, 
which, after a few convolutions, passes to the anus situated in the centre of 
the back. The digestive canal is a caecum given off by this last, and 
has many spiral turns in the cavity of the body.” 
In the Holothurioidea, the very muscular pharynx is surrounded by 
the osseous circle. In the Holothurinae, the intestinal canal, which is long 
and equal throughout, has many turns from behind forwards, ending at 
last in a large cloaca situated at the posterior part of the body. But in 
the Synaptinae, it is short and nearly straight, and terminates in an anus 
having no cloaca. 
In the Echiuridae “ this canal closely resembles that of the Synaptinae. 
In the Sipunculidae it is long, making its first turn about the middle of 
the body, and its second near the posterior extremity. The ascending 
and descending portions of this last pass spirally around each other on 
their way to the anus which is situated on the ventral surface of the 
body. 
§ 86. 
As to the glandular appendages of the alimentary canal, the salivary 
organs are perhaps entirely wanting in these animals. 
In the Holothurinae alone, are there particular appendages opening into 
its anterior portion, which could be regarded as organs of this nature. In 
the different genera, species, and even individuals of this family, these 
appendages widely vary as to form and number. 
is 5 Miller, Abhandl. d. Berl. Akad. 1841, p. 230, 
‘af. V. 
6 See Meckel, Syst. d. vergleich, Anat. IV. p. 
55, and Delle Chiaje, Memor. &c. Tay. XXV. 
fig. 12; also Carus and Otto, Erlauterungstafeln 
z. vergleich. Anat. Hft. IV. Tab. I. fig. 25, and 
Wagner, Icon. zoot. Tab. XXXII. fig. 8. The 
nature of the canal figured by Delle Chiaje is yet 
unknown. It arises from the first portion of the 
intestine, and returns to it at its middle portion. 
It has not been mentioned by Meckel. 
a 7 oe Monogr. des Scutelles, p. 14, Pl. IIL. 
g. 19, a. 
8 Ibid. p. 17, Pl. XXII. fig. 28 (Laganum and 
Mellita). 
9 See Tiedemann and Valentin, loc. cit. 
10 The digestive canal of the Holothurinae was 
first figured by Delle Chiaje and by Tiedemann, 
loc. cit. ; afterwards by Quoy and Gaimard (At- 
las zool. du Voyage de l’Astrolabe. Zoophytes, Pl. 
VI. fig. 2, Pl. VIL. fig. 3). The cloaca is always 
wholly attached to the skin by numerous tendinous 
fibres. In Chirodota fusca the intestine is spiral 
(Atlas zool. &c. Pl. VIII. fig. 3); but in Synapta 
Duvernaea it is nearly straight (Quatrefages 
Ann. d. Sc. Nat. loc. cit. Pl. I.). 
1 See the remarks of Forbes and Goodsir upon 
the Anatomy of Thalassema and Echiurus (Fro- 
riep’s neue Notizen, No. 392, p. 273, fig. 12). 
22 The alimentary canal of Sipunculus nudus, 
and of Echinorhyncus, has been faithfully de- 
scribed by Delle Chiaje (Memor. &c. I. p. 9, Tav. 
I. fig. 5, 65 p. 126, Tav. X. fig. 11) and Grude 
(Miller’s Arch. 1837, p. 245, Taf. XI.). I have 
found a similar intestine in Phascolosoma granu- 
latum. 
