t.K) MARINE BIOLOGY OF THE SUDANESE RED SEA. 



to tbe (JifEerent degrees of contraction, and is therefore of no signifioanee. 

 We have referred the specimen to Pallas's species, T. purpurea. From this 

 ir does not seem to us that T. chamissonis can be separated. 



Many of the polyps are crowded with spherical or nearly spherical repro- 

 ductive bodies, most of which show an internal cavity and a wall with several 

 layers of nuclei. The following measurements of diameters were taken in 

 millimetres: 0-0765 X 0-0765 ; 0-136x0-1445; 0-296x0-296; 0-323x0-32:^: 

 0-34x0-351. These will form the subject of subsequent study, along with 

 other bodies of a similar nature which occur in various Alcyonarians. They 

 are either young embryos or sperm-sacs. 



Locality. — Outer edge of the reef (Shubuk). Previously recorded from 

 the Red Sea, from Zanzibar (as T. chamissonis), and from East Indies (as 

 T. chamissonis). 



Order II. ALCYONACEA, Yerrill. 



Xenia umbellata, Lamarck. 



Numerous colonies with whilish-brown stems and chocolate-brown polyps. 

 Many of the groups are 50 mm. in height, the stem being about 30 mm., 

 and the polyp-bearing region about 20 mm. A common size of polyp is 

 10-12 mm., the tentacles and the polyp-body being each 5-6 mm. in length. 

 The polyp-bodies and tentacles are thickly covered with glistening calcareous 

 corpu.scles. These are arranged in 8 very distinct longitudinal rows on the 

 polyp-body. Every here and there one observes what looks with low power 

 like a perforation about a millimetre in diameter and uith a perfectly 

 regular contour. These pore-like spots are dense colonies of zoochlorellfe. 

 There are on each side of the tentacles four rows of long pinnules, about 18-20 

 in each row. There are abundant ova. 



While the description just given applies to a large number of colonies, 

 there are many others which differ markedly, e. g. in being much smaller, in 

 showing no spicules or almost none, in ha\-ing some reddish colour, in the 

 Qumber of rows of pinnules, in the total number of pinnules, and in the length 

 of the pinuides. After a careful examination of a large number of specimens, 

 we have come to the conclusion that these are all referable to a very variable 

 species. 



A specimen from the outer part of Suakim Harbour has a peculiar reddish 

 colour, which Mr. Crossland noted as " not natural " ; but it may be recalled 

 that Klunzinger observed a rusty brown on the inner side of the tentacles. 

 In this specimen the body of the polyp is about 10 mm. in length ; the 

 tentacles are about 8 mm. in length ; there are slender, elongated, pointed 

 pinnules in 2-3 rows about 12 in each row. There are very abundant 

 zoochlorellse, and there is not the slightest trace of effervescence when the 

 polyp is dropped into dilute hydrochloric acid. 



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