CORAL PIGMENTS. 189 
were much darker than those dredged from a depth of 40 fathoms, and what is of great 
importance, the side of the corallum next the surface, and therefore more exposed to 
sunlight, was a deeper blue than the opposite side. 
5. REMARKS ON THE CoRAL PIGMENTS. 
Of the above pigments some belong to those which may be called chlorophylloid, 
whether they are intrinsic to the coral, whether they are digestive products, or whether 
they are due to the presence of symbiotic algae. The other pigments found being probably 
“lipochromoids” and “melanoids.” These latter were first described by the late Professor 
Krukenberg’. The occurrence of the chlorophylloid pigments is of great interest. Prof. Sidney 
Hickson has expressed the opinion that corals probably contain chlorophyll or an analogous 
substance, I may refer to the paper of the late Professor Krukenberg again in this 
connection, “Die Farben der lebenden Korallen des Rothen Meeres,’ in which he describes 
a chlorophylloid pigment in various fresh corals. In stating that this pigment is a “hepato- 
chrome” (or an enterochlorophyll) he is however not correct, as can easily be proved. The 
greater abundance of helioporin in the surface exposed to sunlight, and its diminution, or 
even absence, on the lower surface of the corallum, and further its apparent relationship to 
a chlorophylloid substance, is of great interest. 
Doubtless these pigments are of physiological importance to the corals, as Prof. Hickson 
infers. And the dark pigments referred to above when in solution have the property of 
arresting the ultra-violet and violet rays of light: in this way they probably act as a 
screen, protecting the delicate organisms from the imitating effects of the rays of short 
wave-length. 
The pigments, then, of the above corals are either chlorophylloid, or of a closely 
connected kind of pigment, which latter absorbs the violet end of the spectrum, and seems 
generally changeable into the next kind, by the agency of heat, etc., namely, into the dark 
pigment which gives the coral its dark colour in the fresh condition: e.g. brick-red, as 
in C. willeyi, or cloth-black, as in C. nigrescens, or velvet-black, as in Dendrophyllia ramea. 
This dark pigment is, as said above, extractable from the decalcified corallum by means of 
caustic alkali in aqueous solution. I would call attention more especially to the absence 
of lipochromes, even in the case of the corals possessing a chlorophylloid pigment, and to 
the presence of the peculiar pigments in some corals, which while being soluble in fat 
solvents like the lipochromes, yet instead of giving the lipochrome reaction, give a red 
reaction with nitric acid, sulphuric acid and iodine in potassium iodide solution. 
6. INTEGUMENTAL PIGMENT OF A RED ASTEROID (Ophidiaster cylindricus’*). 
The specimens were preserved in pure 70 per cent. spirit and were more or less 
mottled of a bright red colour. As the spirit was colourless it was evident that the 
specimens did not owe this colour to a red lipochrome so common among starfishes found 
in British seas. (MacMunn.) 
1 Centralbl. f. d. med. Wissenschaften, 1883, No. 44. 3 [I am indebted to Prof. Jeffrey Bell of the British 
2 See 4 Naturalist in North Celebes, pp. 149—151. Museum for this identification. Ep.] 
