ON COLOURING MATTERS OF VARIOUS ANIMALS. 7 
line band. In a very strong solution, or with weak trans¬ 
mitted light, the broad band appears to extend the entire 
distance from the alkaline band in the extreme red to D, 
whilst the entire violet and blue end of the spectrum is 
absorbed continuously as far as b. 
By very cautious neutralisation of the solution a green 
fluid can be obtained, which yields both acid and alkaline 
spectra showing four bands (PL I, fig. 5 d). In it the ex¬ 
treme red band of the alkaline solution and the intense band 
in the region oi I) of the acid solution arc seen of equal 
intensity, whilst the second band of the acid spectrum 
is very faint. In the exactly neutral solution thus yield¬ 
ing four bands, acid and alkaline pentacrinin appear to 
coexist. 
The acid solution of pentacrinin, when slowly evaporated 
and concentrated, yields a precipitate, which, when collected 
and dried, appears as a dark violet-coloured amorphous 
powder. 
This substance, viewed by transmitted light as adhering 
to the filtering paper, and rendered transparent with glycerine, 
yields the same spectrum as the acid solution. 
The dried colouring matter is very sparingly soluble in 
absolute alcohol, but freely soluble in this, on the addition 
of a few drops of hydrochloric acid. It is not soluble in 
dilute hydrochloric acid alone, requiring the addition of 
alcohol to show the spectrum. 
The fresh colouring matter is soluble in fresh water, but 
remains partly suspended, forming a slightly opaque dark 
purple solution, which gives, when quite fresh, a mixed acid 
and alkaline spectrum. When the aqueous solution is acidi¬ 
fied the colouring matter becomes entirely dissolved, and 
the fluid becomes clear and transparent, and of a beautiful 
pink, yielding the same spectrum as the acidified alcoholic 
solution. When the intense watery solution is rendered 
alkaline a green flocculent precipitate is formed, and in a 
very intense solution the two outer bands, the most refran¬ 
gible and least refrangible, are lost, being encroached upon 
and included iu the general absorption of the ends of the 
spectrum. 
All the specimens of Pentacrinus obtained off the Kerma- 
decs, which were probably of two species, were of a uniform 
dusky purple colour when brought to the surface, being 
evidently coloured by acid pentacrinin. 
The specimens obtained off the Meangis islands were 
possibly of lour species. Of these, three forms were simi¬ 
larly coloured dark purple, one being especially dark, whilst 
