ON COLOURING MATTERS OF VARIOUS ANIMALS. 9 
soluble iu weak spirit, and gives an intense fuchsin-coloured 
solution. This, when compared with that obtained from a deep 
sea llolothuiian found to contain the same colouring matter 
(v. inf.), is seen to be much redder, but it becomes pinker as 
diluted with alcohol, and at last quite pink and indistinguish¬ 
able to the naked eye from that of the Ilolothurian. The 
solution when of moderate strength gives a spectrum 
consisting of three well-defined absorption bands (PI. I, 
fig. 9 a). On using a very weak solution and gradually 
strengthening it the least refrangible band, as being the 
most intense, appears first, and is visible in solutions which 
appear very slightly (tinted indeed to the unassisted eye. 
The other two bands appear together. The middle band 
is at first darkest about E. The most refrangible band, which 
is much less dark than the middle one, is of uniform intensity. 
Neither the red nor violet ends of the spectrum are much 
absorbed. 
When the solution is very strong all three bands become 
intense; the violet disappears and all the light, except the 
red and yellow, becomes very faint. The bands remain as 
before, except that the middle band now appears of uniform 
intensity throughout. When the solution is rendered 
stronger still, the least refrangible band extends gradually 
up towards D, and the whole of the spectrum becomes ab¬ 
sorbed, except a band of light, consisting of red with a little 
yellow (PI. I, fig. 2 b). 
On the addition of hydrochloric acid to the alcoholic 
solution the colour changes to an orange, and the spectrum 
now consists of two bands (PI. I, fig. 7 c), one lying to the 
red side of E, the other to the violet side of h and extending 
fo !'• These bands are in weak solutions separated by an 
interval of light. In very intense solutions the bands are 
joined by the absorption at the violet end of the spectrum, 
and the spectrum consists of a simple band of red, yellow 
and green light (PI. II, fig. 9 c). In solutions of inter¬ 
mediate strength the two bands arc connected together by 
a clouding interrupted by lighter streaks, whilst the more 
refrangible band is dark just about the region of F, and has 
its main darkest mass separated from this dark narrow streak 
at F by a lighter interval. 
On the alcoholic solution being rendered alkaline by 
addition of ammonia, it changes its colour to a deep violet, 
and a flocculcnt purple precipitate is formed in it, which 
can readily be separated by filtration. The precipitate 
when dried appears as a violet amorphous powder, which is 
insoluble in alcohol and oil of cloves, and can thus be 
