ON COLOURING MATTERS OF VARIOUS ANIMALS. 13 
yields the spectrum shown (PI. II, fig. 13 b). The ends of 
the spectrum are very little absorbed by either of the two 
solutions. The colouring matters are evanescent and soon 
fade. 
In Bronn’s 1 Klassen und Ordnungcu des Thierreichs’ 1 it is 
stated that the coloured fluid of Aplysia is, when fresh, 
purple red. Hydrochloric acid in small quantities inten¬ 
sifies the purple colour of the fluid, in larger, changes it to 
blue. ITuschke says the fluid contains iodine, but the purple 
colour cannot be derived from this. 
An Italian chemist has recently stated that an anilin base 
is present in Aplysia. 
Doris .—A Doris or example of a closely allied genus 
obtained in lat. 0°33' S.,long. 151°34' W., from 2425 fathoms, 
September 6th, 1875, had the surface of its foot coloured 
of a dark purple, whilst the remainder of the body surface 
was devoid of such pigment. The purple colouring matter 
was found to be soluble in alcohol acidified with hydro¬ 
chloric acid, and both when fresh and in solution gave a 
spectrum showing two well-marked absorption bands (PI. II, 
fig. 14) which resemble those obtained from the acidified 
solution of the colouring matter of Aplysia. 
In the Doris, however, the spectrum of the fresh colouring 
matter is identical with that of the acidified solution. It is 
thus possible that the colouring matter exists in the animal 
naturally in the acid form. 
Ianthinin .—Some large specimens of Ianthina were pro¬ 
cured on the surface of the North Atlantic, on June 20th, 
1873, and afforded an opportunity for the examination of the 
well-known purple-coloured fluid emitted by those animals, 
and for corroborating some observations made previously 
during the voyage. 
The colouring matter in question is soluble in spirit, but 
apparently only to a limited extent, since, if after a number 
of lanthinas have remained for a day or so in spirit, the 
coloured spirit be poured off and fresh spirit substituted, 
the colouring matter is seen to be shed out, and in a dense 
cloud, and this spirit rapidly becomes as intensely coloured 
as the preceding. 
The spirit solution is of a pale pinkish-blue colour when 
viewed by directly transmitted light, but when held so that 
the light reaches the eye from it obliquely it displays a 
most brilliant red fluorescence, in this matter resembling 
greatly JEsculin, which is also blue by transmitted light. 
When examined spectroscopically by transmitted light 
i Bd. Ill, p. 756. 
