ATLANT. DEEP-SEA EXPED. 1910. VOL. III]. 



PENNA.TULACEA. 



In the walls of the polyps we find tripennate spicules up 

 to 075 mm long, smooth and somewhat irregular, with 

 composite ends. The spicules of the sarcosoma of the 

 rachis are similar in form but smaller. The spicules of 

 the inferior part of the rachis and of the stalk are still 

 smaller and acquire a peculiar structure. They are tripen- 

 nate, but because of their granular surface, this character 

 is very often indistinctly seen; they seem to be covered 



a b e d 



Fig. 3. Spicules of Umbellala Giintheri from Stat. 48. 



a: Spicula of the tentacles (X 200). b: Of the polyp body 



(X 100). c: Upper part of the rachis (X 200). d: Outer 



layer of the stalk (X 200). 



all over with irregular wart-like protuberances. This peculi- 

 arity is also mentioned in the "Chailanger" report. In the 

 inner layers of the stalk we find the usual, elliptic corpuscles. 



These observations complete those of Kolliker, and 

 together enable us to give the following diagnosis of 

 Umbellula Giintheri:— 



The colony is provided with a thin, stiff stem. The 

 upper part of the rounded stalk becomes a little thicker 

 and quadrangular. The rachis is very thin and quadrangular, 

 like the axis, which has concave sides and rounded edges. 

 Just below the cluster of polyps the rachis expands and 

 is laterally flattened. The secondary polyps are situated 

 a little beneath the terminal polyp, five in a semicircle, 

 leaving free a broad, dorsal space. The larger polyps are 

 broad and cylindrical, with tentacles as long as the body. 

 The zooids, distributed here and there on the thin part 

 of the stem, are almost invisible and without any trace of 

 tentacles. On the swollen upper part of the rachis they 

 are large and wart-like, filling every interspace between the 

 bases of the polyps. The sarcosoma is studded all over 

 with tripennate spicules, which attain a length of 0-6 mm 

 in the tentacles of the polyps, 0-75 mm in the walls of 

 the polyps, and 0-25 mm in the stalk where they are 

 covered with wart-like protuberances. The stem is yellowish 

 white, the polyps grey with a brownish tinge. Habitat: 

 Abyssal region of tropical Atlantic (and Pacific?). 



Umbellula gracilis Marshall. 

 PL, figs. 2 and 3. 



On the eastern side of the Canaries, at Stat. 41 a 

 complete colony belonging to the group with rounded 

 axes was taken. 



The total length is 574 mm, the lower 56 mm com- 

 prising the stalk which is 8 mm in diameter. The upper 

 thinner part of the rachis is 1-5 mm broad, but expands 

 about 57 mm below the top. Polyps occur 27 mm higher 

 up, and when expanded are 21 mm long and 4-5 mm 

 broad, their tentacles attaining a length of 18 mm. The 

 proportion between stalk and rachis is 1 : 8-8. 



The stalk is almost cylindrical, ending in a short 

 cone; there is no distinct expansion. Numerous zooids 

 appear 56 mm above the base, and we must therefore 

 draw the upper limits of the stalk at this point. The rachis 

 gradually decreases in breadth, till, some 50 mm below 

 the polyps, it attains its smallest breadth. Here the stem 

 is bent in a wide curvature and the cluster of polyps is 

 thus pendulous. The larger polyps are slender and cylindri- 

 cal, with pretty long tentacles. The pinnules of the 

 tentacles are all of one size. 



The arrangement of the polyps does not seem to be 

 very regular. A terminal polyp is found in the cluster 

 at the top of the rachis; although the position is charac- 

 teristic, we find no trace of the axis, either in the wall of 

 the polyp or at its base. — In a circle round this terminal 

 polyp we find 7 secondary ones; the next 9 polyps com- 

 pose an almost indiscernible circle. The last 8 polyps, 

 which are situated proximally to the circles mentioned, 

 show no distinct arrangement in rings. At first we do 

 not see any bilateral arrangement of the polyps. Never- 

 theless a careful examination shows that the proximal six 

 polyps are located in three pairs, leaving free a rather 

 broad dorsal space. Higher up secondary polyps have 

 also budded out in the median dorsal line, thus oblite- 

 rating the bilaterality. 



The zooids fill every interspace between the crowded 

 polyps, where, as well as in the swollen upper part of 

 the rachis under the cluster, they are large and distinct, 

 but it is only with the utmost difficulty that they can be 

 traced in the thinner part of the stem. Here and there 

 we see a tiny threadlike tentacle, but in most of the 

 zooids it is missing. It seems as if the zooids of the 

 thinner parts of the rachis were located on the ventral 

 sides; on the dorsal sides none could be discovered. 

 Towards the stalk, where the rachis again attains greater 

 dimensions, the zooids become more visible, and are located 

 all round the stem. They do not, however, again attain 

 the dimensions of those in the expanded upper part of 

 the rachis. 



