28 THE VOYAGE OF H.M.S. CHALLENGER. 



dual fio-ured by Sars' they occur on the lowest thirty-three joints of a stem with fifty- 

 nine joints altogether. In another case five out of eighteen joints are cirriferous ; while 

 the individual represented in PL IX. fig. 1 has only nine cirriferous joints in a stem of 

 over forty. A similar variation occurs in Khizocrimis raivsoni. Every joint in the 

 lowest part of the stem may bear cirri at one or both ends of the long axis of its upper 

 face. But I have in no case found more than fifteen joints in this condition, and they 

 are sometimes not consecutive, a cirrus-less joint being occasionally interposed between 

 two others which bear cirri (PL X. fig. 15). On the other hand, in the only individual 

 with a complete stem which was obtained by the Challenger, and also in the young 

 specimens dredged by the " Porcupine," there are no radicular cirri at all, but only a 

 spreading root formed by subdivision of the main axis of the stem (PL LIII. fig. 7) ; and 

 this appears to be a constant condition in Bathycrimis (PL VII. figs. 1, 9 ; PL Villa, 

 fig. 3). 



Below the last of the regular and dice-box shaped joints, which may or may not bear 

 cirri, there come one or more others of irregular shape and variable size. Spreading 

 rootlets proceed outwards from these, as a rule more abundantly in Rhizocrinus than in 

 Bathycrinus. In Rhizocrinus lofotensis this inferior joint usually bears several slender 

 root filaments disposed around a central one ; while one or two stronger and branching 

 rootlets sometimes come ofi" between it and the regular stem-joints. This is more 

 especially the case in Rhizocrinus rawsoni ; but in Bathycrinus the inferior joint, or " root- 

 joint " as it has been called, is quite short, and gives ofi" two or rarely three chief roots, 

 which themselves subdivide into smaller ones (PL VII. figs. 1, 9 ; PL Villa, fig. 3). 



Both these rootlets of the stem-axis itself and the radicular cirri are composed of a 

 series of gradually diminishing joints closely united by ligaments. They attach them- 

 selves to foreign bodies by calcareous expansions round their ends or beneath the sides on 

 which they happen to rest (PL IX. fig. 1 ; PL X. fig. 15). Anything serves for this 

 purpose which may improve the anchorage of the Crinoid in the soft mud, which is nearly 

 universal at great depths, e.g., fragments of shell, grains of sand, sponge-spicules, foramin- 

 iferal tests, &c. Hence, whatever be the case in the Pentacrinidse, Rhizocrinus and 

 Bathycrinus must remain permanently fixed in one place throughout life. 



In a specimen of Rhizocrinus raivsoni which was dredged by the " Travailleur," and 

 was described as a new genus Democrinus by Perrier,^ the diameter of the stem is lessened 

 at the origin of two groups of rootlets, and regains its former size lower down. Perrier 

 suggests the question " si la partie qui se prolonge au delk des racines n'est pas destinee a 

 devenir un second pedoncule surmonte d'un second calice. Si cette induction se verifie, 

 les Democrinus constitueront le premier exemple actuel d'Echiuodermes vivant en 



• Op. cit., tab. i. fig. 1. 



' Sur un nouveau Crmoide fix^, le Democrinus Parfaiti, provenant des dragages du " Travailleur," Comptes rendus, 

 t. scvi,, No. 7, pp. 450, 451: 



