ON COLOURING MAtTERS OP VARIOUS ANIMALS. 9 



soluble in weak spirit, and gives an intense fuchsin-colourecl 

 solution. This, when compared with that obtained from a deep 

 sea Holothurian 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 Holothurian. 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, Avhich 

 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 (PL I, fig. 7 c), one lying to the 

 red side of E, the other to the violet side of b and extending 

 to F. 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 (PL II, fig. 9 c). In solutions of inter- 

 mediate strength the two bands are 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 flocculent purple precipitate is formed in it, which 

 can readily be separated by filtration. The precipitate 

 when dried appears as a violet amorphous powder, Avhich is 

 insoluble in alcohol and oil of cloves, and can thus be 



