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



vided with such a pentact and distal ray, always alternates both in the longitudinal and in 

 the transverse direction, as in Euplectella suherea, with an intersection without a pentact. 



Both the tangential rays and the basal portion of the distal ray are surrounded by 

 numerous greatly extended comitalia which are for the most part triacts. Over the 

 meshes of the lattice-work which are not perforated by parietal gaps, there extend spiral 

 strands of thin, elongated parenchymalia, which cross each other obliquely, and which are 

 also for the most part triacts. 



In the circular membrane which surrounds every parietal gap there occur near the free 

 inner margin numerous short blunt monacts of a sceptre-like form, whose five reduced 

 rays project at the one end as short rounded stumps or hemispherical knobs (PL VI. fig. 5). 

 The occurrence of this form has induced 0. Schmidt to dedicate the species to Jupiter. 

 Besides the fully formed sceptre spicules numerous diacts also occur with projecting 

 cruciate axial knots, which show very clearly how the sceptres have arisen. 



More characteristic than those sceptres, which also occur singly in Euplectella 

 suherea, are the clasps or fibulae which are scattered with comparative uniformity 

 throughout the whole parenchyma of Euplectella jovis. These exhibit a straight, thick, 

 middle portion with a central node and two curved hook-like terminal rays which run out 

 to fine points (PI. VI. fig. 5). The latter are as a rule clearly marked ofi" from the middle 

 part, but their curves usually lie in difi"erent planes, turned towards opposite sides, so that 

 when seen in a certain direction they seem to present the figure of an S. I regard these 

 clasps, which I also met with in Holascus fihulatus, as derived from oxyhexasters with 

 bent terminal rays. I do not derive them from simple hexacts, because on each side a 

 terminal ray springs from the corresponding principal ray. Important also in this respect 

 is the generally very clearly developed median node, on which four lateral tubercles may 

 sometimes be seen. Here and there triacts or tetracts may also be seen whose rays have 

 the same form as in these diact fibulae. This interpretation also harmonises ^uith the, 

 fact that in Euplectella jovis the oxyhexasters which are present in all other species of 

 Euplectella do not occur, but are, as might be expected, converted into the clasps. 



On the outer surface of the distal ray of the sword-hke hexact-hypodermalia, large 

 floricomes occur with a small number of terminal claws exactly as in Euidectella suherea. 



5. Euplectella owenii, Herklots and Marshall (PL VI. figs. 1, 2). 



1868. Herklots and Marshall, Arch. Neerl. des sci. nat., iii. jx 435. 



1875. Marshall, Zeitschr. f. wiss. Zool., Bd. xxv., SuppL, p. 142. 



1876. Marshall, Zeitschr. f. wiss. Zool., Bd. xxvii., p. 113. 



Of that elegant Japanese Euplectella, which was first described by Herklots and Mar- 

 shall and named Euplectella oiceni, no specimens were brought home by the Challenger 

 Expedition. There occurs, however, a relatively well-preserved specimen of this species 

 among those Japanese Hexaetinellida which were handed over to me by Dr. Doderlein of 



