
188 c. A. MACMUNN. 
4. HELIOPORA COERULEA} 
On extracting the coarsely-powdered, dry coral with alcohol a solution of a bluish-green 
Alcohol extract Colour was obtained which had a red fluorescence. This showed a band in 
of dried coral. the red from 2670 to 644, 
The solution was evaporated at the temperature of the air, and left a blue-green residue. 
Redissolved in absolute alcohol a blue-green solution was obtained, which had a_ red 
fluorescence and showed four absorption bands which read:—Ist, from 674 to 1635, including 
shadings, 2nd a shadow from 2616 to 1592, 38rd from 27577 to 560? and 4th from 545 
to 1531. This spectrum denotes the presence of a chlorophylloid substance, but it was 
not accompanied by a lipochrome. 
The powdered coral, already extracted with alcohol, was decalcified as before. The acid 
solution appeared blue but this was found to be due to particles in suspension 
as it disappeared on filtering. On extracting the decalcified blue parts of 
the coral with rectified spirit a fine blue solution was obtained, like ammoniated 
sulphate of copper solution. This solution showed no absorption band, but transmitted the 
blue, green, and yellow of the spectrum and cut off a portion of the red end. Caustic 
soda discharged a part of the blue colour but did not destroy it. 
The pigment of 
the decalcified 
coral. 

A deep layer of neutral spirit solution of helioporin—as we may call it—more or less 
absorbed the red end of the spectrum up to and beyond the D line. 
On evaporating such an alcoholic solution on the water-bath a blue residue was left. 
This was insoluble in ether, in chloroform, and in water, soluble in alcohol, but not as 
freely as before it was evaporated by means of heat. A further confirmation of the change 
undergone by the pigment in solution by heating was shown by the appearance of a band 
in red and one in the yellow at the D line. These bands reminded one of the chlorophylloid 
spectrum of the alcohol extract of the dried, undecalcified coral, and probably point to the 
connection between helioporin and this chlorophylloid pigment. Such a solution changed 
further on standing exposed to the air to a purplish tint, but still showed the two 
absorption bands referred to above. 
Moseley, who first described this blue pigment of Heliopora?, says that nitric acid destroys 
the blue colour of Heliopora. I found that nitric acid added to the alcohol solution made 
the colour more lavender, but did not remove it. Hydrochloric acid made the colour bluer. 
Caustic alkalies change the colour to a dirty green, as Moseley described. Here again no 
lipochrome bands could be detected. 
This blue pigment decreases as the depth increases in which the coral lives; thus in the 
specimens sent me I found that the greatest amount of helioporin was present in specimens 
from the reef, which were coloured dark blue. Those dredged from a depth of 25 fathoms 
1 [In this case the pigment is situated in the corallum outer reefs of the atolls of the Maldives, and was obtained 
which is completely external to the living tissues. Most of also in various dredgings between 25 and 45 fathoms. On 
the specimens, submitted to Dr MacMunn, had been cleaned the outer slope of Addu Atoll it seemed the most important 
by exposure for a long period of time to the sun and rain. _ reef builder at the depth of 40 fathoms. Ep.] 
The genus is found sparingly on the sand flats within the 2 Quart. Jl. Micro. Sc. vol. xvut. N.S. p. 2. 
