UMBELLULIDAE 255 



U. huxleyi Kiikenthal & Broch 191 1, p. 290, PI. 21, fig. 54. 

 U. gracilis Broch 19 13, p. 6, PI. i, figs. 2, 3. 

 U. huxleyi+ U. gracilis Kiikenthal 1915, p. 53. 

 U. huxleyi Hickson 19 16, pp. 122 seq. 

 Non-U. huxleyi Hickson 1937, p. 119. 



This species was described by KoUiker from the 'Challenger' Expedition. In his report he men- 

 tions four specimens (A-D), one of which (C) is missing,* whereas the other three are in the collec- 

 tions of the British Museum (Nat. Hist.). The specimens, which according to their size and structure 

 must be his A and B, have quadrangular axes; they are evidently young specimens of U. lindahli; 

 they are discussed under this species on page 264. It is, however, quite clear that Kolliker really 

 based his work on the largest specimen D, which he carefully described and figured. Specimen D has 

 accordingly been selected as lectotype of U. huxleyi. 



Kolliker wrote: 'Axis indistinctly quadrangular', evidently basing his definition on specimens A 

 and B, caught in the same haul and assigned to the same species as D. (As mentioned above, these 

 two specimens have now been assigned to U. lindahli.) The axis of the lectotype D is round throughout 

 in section; the holdfast ('stalk'), which according to Kolliker is 34 mm. long, is also round. The axis 

 is only very little thicker than the ' stem ' and without any hint of quadrangularity. The thickening of 

 the 'stalk' is due to greater development of the coenosarcal tissues which show some longitudinal 

 wrinkles, suggesting a more or less angular section in the part shortly above the ' bulb '. 



Kolliker assumed that the species was 'indistinctly bilateral in the fully developed stage'. Kiiken- 

 thal (191 5) on the other hand wrote: 'Die Zooide. . .stehen. . .am Schopfkelch dichter und nur ein 

 dorsales Feld freilassend, gehen aber nicht auf das von den Polypen umschlossene innere Feld iiber '. 

 In young specimens also this seems to be partly the case. Kolliker's type specimen D has no naked 

 field dorsally between the siphonozooids on the swollen rachis below the autozooid cluster, and 

 although siphonozooids are apparently absent between the bases of the autozooids in the lectotype, 

 they have been observed in this position in larger specimens than those from the 'Challenger' 

 and 'Valdivia' Expeditions. These two specimens are of about the same size, 180 and 193 mm., 

 respectively, but the polyp clusters differ markedly in the development of their autozooids. The lecto- 

 type has 18 autozooids, ranging from mere buds to fully developed polyps; but a primary polyp is not 

 distinguishable, and it is impossible to describe any arrangement in whorls. The ' Valdivia ' specimen 

 had only 6 autozooids. The dorsal one, which was a little smaller and placed a trifle above the circle, 

 was considered to be the primary polyp ; the autozooid to the left of the primary polyp was also a little 

 smaller than the other four secondary autozooids. Nevertheless, the ' Valdivia ' specimen evidently 

 belongs to the same species as the ' Challenger ' lectotype of U. huxleyi. 



U. gracilis Marshall, from the 'Triton' Expedition, is also probably synonymous with this species 

 although two of Marshall's statements might seem contradictory. He says (1883, p. 143): 'Stem 

 cylindrical along the greater part of its length, becoming quadrangular in the terminal dilated part.' 

 A glance at his drawing (1883, PI. 25, fig. 29) shows at once that Marshall does not refer to the axis but 

 to the entire stem and holdfast, and that he is really describing the longitudinal furrows caused by 

 contraction of the ample tissues surrounding the lower and somewhat thickened part of the (round) 

 axis. Marshall does not especially confine himself to the axis but uses the confusing phrase 'the 

 stem or calcareous axis'. Here, however, we must remember that the four longitudinal main canals 

 of the stalk-tissues (when contracted) always cause the thicker holdfast to appear more or less 

 distinctly square, independently of the shape of the axis, whether round or square. 



* See footnote, p. 253. 



