50 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
to the different degrees of contraction, and is therefore of no significance. 
We have referred the specimen to Pallas’s species, 7. purpurea. From this 
it does not seem to us that 7. 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°136 x 0°1445; 0°296 x 0°296; 0°323 x 0°323; 
0:34 0°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 JT. chamissonis), and from Hast Indies (as 
T. chamussonis). 
Order II. ALCYONACEA, Verrill. 
XENIA UMBELLATA, Lamarck. 
Numerous colonies with whitish-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 abont 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 
corpuscles. 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 with a perfectly 
regular contour. These pore-like spots are dense colonies of zoochlorelle. 
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 having some reddish colour, in the 
number of rows of pinnules, in the total number of pinnules, and in the length 
of the pinnules. 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 
zoochlorelle, and there is not the slightest trace of effervescence when the 
polyp is dropped into dilute hydrochloric acid. 
