PENNATULIDA. 85 



exceptions, i. e. abnormalities : ) , as it seems everywhere else in the octactinia to be a law that the 

 eight arms of the polyps are formed at the same time. 



It has already been stated above that Umb. encrinus is not quite devoid of spicules, as has 

 always been maintained hitherto. Just as in the preceding species and in some others, the lower 

 end of the peduncle has indeed numerous, but very small spicules which cannot be seen with the 

 lens. These spicules (PI. Ill, fig. 51) are sometimes oval, 0.012 o.oi6 mm long, and o.oo8 mm broad, 

 sometimes somewhat dumb-bell-shaped, sometimes finally, small, and combined into numerous groups 

 of four measuring o.on mm . Some of the oval spicules show an indication of the common triangular 

 form of the Pennatulids. I have seen no spicules in other parts of the colony 



With regard to the construction of the polyps I may mention that the tentacles are not so 

 long in proportion to the body of the polyp as in the preceding species. These organs, to be sure, 

 are exceedingly variable as to length, and their chance degree of contraction plays, of course, a very 

 great part; but in the preserved specimens they are upon the whole of about the same length as the 

 bodies of the polyps sometimes somewhat longer, sometimes somewhat shorter, but never, for 

 instance, more than twice as long. 



Of the sexual organs Danielssen 1. c. p. 51, states the following: The generative organs 

 develop themselves on the gastral filaments, a circumstance, that in a material degree differs from what 

 has previously been known relative to Pennatulidce, where the sexual organs are developed on the septula. 

 Later, on p. 52, it is said: A11 of the eight gastral filaments are occupied by sexual organs; but, upon the 

 two dorsal ones, they begin a little lower down than on the other six. I cannot corroborate these state- 

 ments. The two dorsal septa do not bear sexual organs here, any more than in other octocoralla. These two 

 septa are as always narrower than the others, and their mesenteric filaments arising from the ectoderm are 

 of a simpler form than in the other septa: they form a finely sinuous line running from the base of the 

 stomodaeum along the edge of the septum. They retain the same appearance through the whole gastric 

 cavity of the polyp-body, and into the continuation of this cavity in the rhachis; here they cease, but 

 their septa still continue some way without filaments. All the other 6 septa, on the other hand, carry 

 sexual organs; these septa have thick, much folded endodermal mesenteric filaments which begin at 

 the stomodseum, but reach only a little way down on their respective septum, when they are replaced by 

 the sexual organs, which accordingly take their place on the edge of the septum; the filaments as such 

 have dissappeared in this region. In a polyp whose body is 65 mm long (from Nr. 7, a $), the much 

 folded mesenteric filament occupies a space of 8 mm , then it is finely sinuous for quite a short space, 

 almost as in the two dorsal septa, and the sexual organs then succeed. The sexual organs remind 

 one of grapes, composed of small clusters, often of groups' of three sexual organs (testicles or eggs), 

 and the middle one is the oldest and most developed. Accordingly, the sexual organs are here in 

 all essential features as in other Penuatulids. Marshall has in Umb. gracilis (= lindahlii} also found 

 the six septa carrying genital organs below the filaments (1. c. p. 144); when, however, in his figure 

 (PI. XXV, fig. 34) he makes the sexual organs occupy a relatively considerable part of the lateral sur- 

 face of the septum, this is hardly correct, and does not, at all events, agree with U. encrinus. In 

 U. thomsoni, Kolliker (Festschr. Phys. med. Ges. Wurzb. 1875, p. 9) states that two pairs of .filaments*, 



J ) We know from Penn. phosphorea (and Virg. mirabilis) that zooids may turn into polyps, but only as an exception. 



