HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



The sarcosoma contains no spicules with the exception 

 of the characteristic elliptic calcareous corpuscles in the 

 inner layers of the stalk, which are found in all Penna- 

 tulida. 



It might at first be supposed that the colony above 

 described should be referred to a new species. Among 

 the Atlantic species of Umbellula, we have, according to 

 Jungersen 1 ) only two species without spicules, viz. Um- 

 bellula Lindahli Kolliker and Umbellula encrinus (Lin.). 

 These species have quadrangular axes. Among the syno- 

 nyms of Umbellula Lindahli, Jungersen placed Umbellula 

 gracilis Marshall, though this species from the warm area 

 of the Faroe channel 2 ), is said to have a rounded axis. 

 I do not agree with Jungersen, but am inclined to consider 

 the species described by Marshall as identical with the 

 one represented here, the only difference being that Mar- 

 shall's younger colony had an indistinctly quadrangular 

 terminal dilated part. I therefore separate Umbellula gracilis 

 from the synonyms of Umbellula Lindahli as a distinct 

 species, the diagnosis being as follows: — 



"The colony is provided with a slender and flexible 

 stem. The stalk is cylindrical or indistinctly quadrangular. 

 The rachis tapers off gradually, till it attains its minimum 

 diameter a little below the cluster, where it is so bent as 

 to make the polyps pendulous. The rachis and axis are 

 both round. The numerous polyps are arranged in a dense 

 cluster, which appears to be indistinctly bilateral; the axis 

 of the expanded upper part of the rachis cannot be seen 

 externally. One or two circles of secondary polyps can 

 be traced round the terminal one. The polyps are cylin- 

 drical and slender with tentacles shorter than the body. 

 The zooids are crowded all round the swollen lower part 

 of the rachis; higher up they are apparently located in 

 lateral series, and are again numerous on the expanded 

 upper part, where they are larger and fill every interspace 

 between the bases of the polyps; they have a thin tentacle, 

 often with pinnules. Spicules are wanting except for the 

 elliptic corpuscles in the inner layers of the stalk.— The 

 stalk is (when preserved) yellowish brown, the thin rachis 

 yellowish white, the polyps dark bluish or greyish brown. — 

 Habitat: Abyssal region of the Atlantic Ocean (warm area). 



Pennatula acu/eata Danielssen. 



This species was taken by the "Michael Sars" on both 

 sides of the Atlantic, at the southern edge of the New- 

 foundland bank (Stat. 70) and on the Atlantic slope 

 southwest of Ireland (Stat. 95). The colony taken on 



the American side of the ocean measured only 54 milli- 

 metres in length, and must thus be characterized as a 

 young colony, while the two specimens, taken at a great 

 depth on the European side are large; the smaller one 

 is 171 mm long, but the larger one is not entire. 



An interesting study is furnished by the small number 

 of larger dorsal zooids, especially in the large colonies 

 from Stat. 95. Both in the small colony from Stat. 70 

 and in the larger ones from Stat. 95 we find about five 

 small zooids on each side of the median line in the middle 

 of the rachis; the number of larger zooids is also constant, 

 and we find in the same place only two on each side of 

 the median dorsal line. The agreement in the development 

 and arrangement of the larger dorsal zooids in the two larger 

 colonies would seem to speak in favour of their belonging 

 to a separate form of the species. The larger dorsal zooids 

 attain a greater length than the calyces of the polyps, as 

 long as 3 or 4 mm. At the base of each leaf we find 

 a very large zooid, which is situated in the same place 

 as the larger dorsal zooids of Pennatula rubra Ellis. 



All the same I cannot consider these characters suffi- 

 cient for separating a new form or variant, in as much 

 as Jungersen 3 ) describes or enumerates many inter- 

 mediate stages between the variants here spoken of, and 

 he points out that the larger dorsal zooids ("aculei") are 

 more developed in the greater depths of the ocean. But 

 as they increase in size they are reduced in number. We 

 might therefore perhaps find it reasonable to speak of 

 biophysically determined forms. On the other hand we 

 find no natural limits which, in this case, might justify 

 the separation of the two "forms". 



The development of biophysically determined variants 

 has caused us to distinguish them according to the depths 

 at which they are found. But, at the same time, as the 

 intermediate stages do not decrease in number, two 

 separable groups of variants (i. e. "forms") cannot be 

 distinguished in regard to habitat. 



Remarks on biology and geographical 

 distribution. 



The observations made on board the "Michael Sars" 

 concerning the phosphorescence of Umbellula Giintheri 

 recall those made on board the "Challenger". These half- 

 forgotten researches 4 ) have passed unobserved by most 

 recent investigators of the Pennatulida, but they give us 

 some idea of the physical character of the light produced by 

 these interesting and typical deep-sea animals, and I there- 



J ) Jungersen: I. c. 1904, p. 71. 



2 ) Marshall: Report of the Pennatulida dredged by H. M. S. "Triton", Trans. Roy. Soc. Edin. Vol. 32, 1887, p. 142 plate XXV, figs. 29—35. 



3 ; Jungersen, I. c. 1904, p. 11. 



*) Wywille Thomson: Voyage of H. M. S. Challenger, The Atlantic, Vol. 1, 1877, p. 151. 



