ON COLOURING MATTERS OF VARIOUS ANIMALS. 3 
water, glycerine, alcohol, and ether, also in strong solu¬ 
tions of ammonia or potash, and it is not affected by picric 
acid. When treated with moderately strong hydrochloric, 
nitric, or sulphuric acids the colouring matter is dissolved 
and yields on addition of water or alcohol a solution of a 
peculiar pink colour, which is markedly dichroic, appear¬ 
ing green in certain lights. This acid pink solution yields 
when very strong a broad intensely black band, which in¬ 
cludes the D line, and which is continued towards the violet 
end of the spectrum as a less intense additional shading. 
When the solution is slightly weakened a narrow interval of 
light divides the black band into two (PI. I, fig. 3 b), and 
when it is still further reduced in strength the interval 
between the bands becomes wider ; the more infrangible 
band becomes much more intense than the narrower one on 
its red side, and the fainter shading on the violet side of the 
more refrangible band is lost (PI. I, fig. 3 c). When the 
solution is very weak indeed one band only, the more re¬ 
frangible of the two, remains. On addition of alkalies to 
the acid alcoholic solution the colouring matter is precipitated 
as a dark burnt sienna-coloured flocculent deposit which 
yields the original three-handed spectrum of the fresh sub¬ 
stance, and is redissolved by acids. The precipitate can be 
separated by a filter and the colouring matter thus obtained 
in the pure condition. When dried it appears as an amor¬ 
phous brown powder, which appears to have all the proper¬ 
ties of the recent colouring matter. 
Polyperythrin was first observed .in a species of Cerato- 
troclius ( C . diadema, n. sp., H. N. M.), which was dredged 
on July 10th, 1873, between the Azores and Madeira. It 
appears to be constantly present in various species of the 
genus Flabellum, and gives the red tint which is present in 
the calcareous corallum of many of these, and which is un¬ 
impaired by maceration of the corallum in strong caustics. 
A large series of Flabellum variabile (Semper) was ob¬ 
tained by the Challenger in the Arafura Sea in GO fathoms. 
Some of the corals had their soft tissues uniformly coloured 
of a dark madder. In others the colouring matter was 
present only in more or less marked streaks, whilst very many 
specimens were entirely (devoid of pigiment, and of a uniform 
white, in fact albinos. 
In most of the specimens the corallum was tinged with 
the colouring matter, but in some it was pure white. 
Polyperythrin has been observed in the following Cce- 
lenterata. 
Ceratolrochus diadema, dredged off Pernambuco, Brazil, 
