ON COLOURING MATTERS OF VARIOUS ANIMALS. 13 



yields the spectrum shown (PL II, fig. 13 b). The ends of 

 tlie spectrum are very little absorbed by either of the two 

 solutions. The colouring matters are evanescent and soon 

 fade. 



In Bronn's ' Klassen und Ordnungen des Thierreichs'i it is 

 stated that the coloured fluid of Aplysia is, Avlien fresh, 

 purple red. Hydrochloric acid in small quantities inten- 

 sifies the purple colour of the fluid, in larger, changes it to 

 blue. Huschke 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' ^Y., 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 (PL 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. 



lanthinin. — Some large specimens of lanthina were pro- 

 cured on the surface of the North Atlantic, on June 20th, 

 18To, and aff'orded an opportunity for the examination of the 

 well-known purple-coloured fluid emitied 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 TEsculin, which is also blue by transmitted light. 



When examined spectroscopically by transmitted light 

 1 Bd. Ill, p. ?56. 



