§$ 78. THE ECHINODERMATA. 8k 
chiefly locomotive; for from them numerous points are prolonged, by 
which they adhere to objects, and to which they become afterwards fixed 
by their sucker. They are covered with ciliated epithelium, and their 
suckers are made firm by a coarse calcarcous network. Elongated cal- 
careous corpuscles of the same nature are found also in their walls, — 
some branching and others hook-like.© 
V. With those Holothuricidea which have them, they have a more or 
less complete sucker, and are scattered irregularly over the entire surface 
of the body, or disposed in regular rows. Usually very short, they can be 
retracted deeply in the skin; but they are capable of equal prolongation, 
and thus perform well the function of suckers.” 
The ambulacral vesicles, which are intimately connected with the circu- 
latory and respiratory systems, will be fully treated hereafter. 
§ 78. 
With the Echinoidea, and Asteroidae, there are other movable organs 
(pedicellariae), which, scattered over the surface of the body, are prehen- 
sile, and used ina pincer-like manner. With the Asteroidae, they usually 
consist of two delicate forceps-like pieces (pedicellariae forcipatae), or of 
two large valvular flaps (pedicellariae valvulatae). Generally they are 
not pediculated.” Those of the Echinoidea have been carefully studied 
in Echinus. They are numerous, and occur for the most part about the 
mouth, presenting three different forms: 1. Those composed of three 
short, lenticular pieces (pedicellariae gemmiformes). 2. Those formed of 
three long delicate pieces, laterally denticulated (pedicellariae tridactyli). 
8. Those with three laterally denticulated spoon-like pieces (pedicellariae 
ophiocephali). They are supported by a base of calcareous, reticulated 
substance; and in the Nchinoidea, always rest upon a stalk, the lower part 
of which contains a cylindrical, calcareous nucleus, while the remaining 
portion is soft, and capable of a spiral contraction.” Here also they are 
covered with ciliated epithelium, and can, by means of movable processes,. 
seize hold of objects, which, being passed along, may be conveyed even 
from the dorsal surface to the mouth. 
near the mouth, and opposite the ambulacral 
rosette, a row of ambulacra having special pores. 
5 See Valentin, Monogr. loc. cit. p. 37, Pl. IV. 
V.,and Erdi in Wiegmann’s Arch. 1842, I. p. 
55, Taf. IL. fig. 10. The corpuscles found by 
Ehrenberg (Abhandl. d. Berl. Akad. 1841, p. 324, 
Taf. IIL. No. VIL. fig. 37, a. b.) in the marine , 
sand of Vera Cruz, and figured under the name 
of Spongolithis uncinata, are only the cruciform 
parts of the skeleton of Echinus. This will be 
evident from comparing them with the calcareous 
corpuscles figured by Valentin (Monogr. loc. cit. 
Pl. V. fig. 65). 
6 Catalogue of the Physiol. series of Comp. 
Anat. contained in the Royal Coll. of Surgeons, 
London, IV. 1838, p. 196, Ph XLIX. fig. 3-5. 
1 With Luidia, there are, however, three tongue- 
like pedicellariae. In Asteracanthion, they have 
a@ soft pedicle. In Asteropsis, Stediaster, and 
*(§ 78, note 2.) See Adams (Ann. of Nac. 
Hist. VII. 1851, p. 237), who has found what he 
regards as Pedicellariae on the skin of Voluta 
Astrogonium, they are valvular and without a 
pedicle; see Muller and Troschel, loc. cit. p. 
10, Taf. VI. fig. 3-6. 
2 The pedicellariae of Echinus were, at first, 
taken for parasitic Polypi by O. F. Muller (Zool. 
Dan. I. 1777, p. 16, Tab. XVI.). See Lamarck, 
Hist. Nat. des Anim. sans Vertébres, II. p. 75. 
More recently, Agassiz (Valentin’s Monogr. loc. 
cit. p. 51) has expressed the opinion that they were 
young individuals. The researches of Delle Chiaje 
(Memor. sulla storia e notom. degli Anim. seuza 
Vertebr. II. 1823, p. 324, Tab. XXIII.) and of 
Sars (Beskrivelser, &c., p. 42, Tab. IX.) upon 
Echinus, Cidaris, and Spatangus, have dispulled 
all doubts as to the real nature of these organs. 
Very correct descriptions of them have lately been 
published by Valentin (Monogr. loc. cit. p. 46, 
Pl. IV.), and by Erdl (Wiegmann’s Arch. loc. 
cit. p. 49. Taf. IL. fig. 1-9).* : 
vespertilio ; he thinks, therefore, that they are 
ind dent parasitic or; — Ed. 
