HOLOTHUEIAN SPICULES 



895 



class generally. 1 But a microscopic examination of their integument 

 at once brings to view the existence of great numbers of minute 

 isolated plates, every one of them presenting the characteristic re- 

 ticulated structure, which are set with greater or less closeness in 



ii;. 680. Holotlmrioidea : I, ,SY/r//o/;/rs Ki'/crstciitii ; rt, calcareous 

 plate of same; b, c, calcareous plates of Holothuria vagabundq ; 

 r7, the same of H. iuJni/i/lis; t>, the same of H. botcllus; f, of H. 

 in: cj, of H. ediilis. 



the substance of the skin. Various forms of the plates which thus 

 present themselves in Holothuria are shown in fig. 68(>. 2 In the 

 Xf/ii(i,])ta, one of the long-bodied forms of this order, which abounds 

 in the Mediterranean Sea, and of which two species (the A', iligitata 



B 



A 



FK;. 6.S1. Calcareous skeleton of Si/ntijitii : A, plate imb.Yldeil in 

 skin ; B, the same, with its anchor-like spine attached ; (', anchor- 

 like spine separated. 



and ,S'. uiha'i-ens) occasionally occur upon our own coasts." the cal- 

 careous plates of the integument have the regular form shown at A. 

 fig. 681 ; and each of these carries the curious anchor-like appendage, 



C, which is articulated to it by the notched piece at the toot, in the 



1 For an account of a very remarkable form see Moseley ' On the Pharynx of an 

 unknown Holothurian, of the family Dendrochirotse, in which the calcareous skeleton 

 is remarkably developed,' Qiuirt. Jaiini. Mimw. Sfi. n.s. xxiv. p. -2 .">.;. 



- For figures of the spicules of British Holothurians, see Bell, Catalogue <if tin- 

 Britixli Echinoderms, London, 1S9-2, pis. i.-vi. 



" 'On the spicules of Si/iittjitii, together with some general remarks on the archi- 

 tecture of Echinoderm spicules,' consult R. Semon, Mitth. Ziiul. Sfu/. \cupcl, vii. 

 p. 27'2. An excellent summary of our knowledge of the spicules of Holothurians is 

 given by Prof. Luclwig in his volume in Broim's TMerreich, pp. ;!5-()l. 



