UMBELLULIDAE 25, 



Hist.)) have autozooids packed with eggs, easily observable through the semi-pellucid, smooth 

 body wall. 



The examination of a very great number of spicule-free specimens shows that the proliferation and 

 arrangement of the autozooids on the rachis afford specific characteristics, as indicated by Kukenthal 

 and Broch in 191 1. Later collections now give grounds for some further systematic regrouping. 



In U. spicata as mentioned above, the rachis is remarkably long, and the autozooids bud irregularly. 

 Siphonozooids of rather large size are crowded in the interspaces all over the rachis. Development 

 results in a long, spaced tassel (PI. I, fig. 2). Another more common developmental series is 

 illustrated by U. lindahli. We might call it the carpenteri-magmflora-antarctica line. In the first 

 stages the budding of autozooids shows a more or less distinctly bilateral arrangement, resulting in a 

 ventral whorl lying distally on the rachis. Gradually the primary polyp is pushed into the central 

 field of the whorl (or the upper part of the whorl dorsally encircles the primary polyp). During this 

 ' magniflora phase ' the short proximal part of the rachis beneath the autozooid whorl generally takes the 

 shape of a bowl on the top of the stem, and in the inner (upper) central field additional autozooids are 

 budded in more or less indistinct whorls. At the same time the distal part of the rachis develops into 

 a short spigot covered all over by autozooids, the bases of which are surrounded by large siphonozooids. 

 This cluster can be regarded as a tassel, although much more concentrated than the spicata type. This 

 antarctica (or encrinus) type is furnished with a distinct, generally rather regular, basal whorl of long 

 autozooids (cf. PI. II, fig. 6). 



In some species, however, the budding of autozooids is restricted to the short distal end of the 

 rachis, and so concentrated that the cluster is more correctly regarded as an almost globose pompon 

 as in U. hiixleyi (PL I, fig. i) or U. pellucida (PI. II, fig. 3). Here the autozooids often seem so 

 crowded that no room is left between them for siphonozooids. 



Umbellula pellucida Kukenthal 1902 (PI. II, fig. 3a, b) 



U. pellucida Kukenthal 1902, p. 593. 



U. purpurea pars Thomson & Henderson 1906, p. 95. 



U. pellucida Kukenthal & Broch 191 1, p. 300, PI. 16, fig. 20; PI. 20, fig. soa-c. 



U. pellucida Hickson 1916, p. 134, PI. 4, figs. 25, 26. 



U. huxleyi Hickson 1937, p. 119. 



This species is one of the small Umbellidae, none of the specimens (about 250) examined attaining 

 a length of 350 mm. and only quite exceptionally exceeding 300 mm. The species is evidently com- 

 paratively common in the Indian Ocean, and prefers lesser depths than most other species of the 

 genus, seemingly above 1600 m., although a single specimen has been caught at 2001 m. depth by 

 the John Murray Expedition. 



' The axis in all the specimens is quadrangular in section : that is to say, it is marked by four shallow 

 longitudinal grooves with four prominent rounded ridges. At the stalk end the ridges become shal- 

 lower, and for a considerable distance the axis becomes almost circular in section. The greatest width 

 of the axis of a large specimen is i mm.', wrote Hickson (1937) who had at his disposal 249 specimens. 



These words at once tell us that the specimens do not belong to U. huxleyi, and examination of 

 these specimens in the British Museum (Nat. Hist.) at once confirmed that they belong to U. pellu- 

 cida. The structure of the axis is quite different from U. huxleyi; it is abundantly incrusted with lime 

 and compact throughout; the stem is therefore only slightly flexible, and in preserved specimens 

 rather rigid and brittle like other species with square axes. 



Kukenthal and Broch (191 1) described the autozooids in pellucida as barrel-shaped. This will 

 depend in part upon the degree of contraction, and Hickson's (191 6) drawings show funnel-shaped 



