106 ERNEST WARRKN. 



that the melanin o£ vertebrates is of the same chemical 

 nature as the black and brown pigments of hydroids and other 

 invertebrates. 



The Nature of the Pigment. 



Our knowledge of the origin and chemical nature of the 

 pigments occurring in animals is still deficient. The black 

 pigment^ commonly known as melanin, found in vertebrates, 

 appears to have a chemical constitution related to that of 

 hasmoglobin. It is certain that the various colouring matters 

 found in invertebrates are not all similar to one another in 

 ■chemical character, and doubtless they differ considerably from 

 the melanin of vertebrates. 



I have tried a few microchemical and other tests on the 

 dark brown pigmented cells of Lytocarpus f ilamentosus, 

 and the following is a sunnnary of the results. In considering 

 these reactions, however, it must be remembered that the 

 specimens had been fixed several years previously with 

 corrosive sublimate and acetic acid. 



(1) The pigment granules had no effect on polarised light. 



(2) Weak acids and weak alkalis of about 20 per cent, 

 ■strength had no definite effect on the granules. 



(3) Alcohol, benzole, oil of cloves, and ether had no action. 



(4) Chlorine dissolved in alcohol decolourised the granules, 

 so also did 50 per cent, hydrochloric acid which had become 

 yellow by the formation of free chlorine. 



(5) Peroxide of hydrogen had a somewhat weak decolouris- 

 ing action. 



(6) Osmic acid did nut appear to intensify appreciably the 

 colour of the granules. 



(7) Millon's reagent tinged red any grainiles which happened 

 to be less dai'k coloui-ed than usual. 



(8) Concentrated nitric acid decolourised the granules 

 instantly, and they became yellow ; the yellow colour Avas 

 intensified by the addition of annnonia. 



(9) A saturated solution of nickel sulphate in annnonia 



