BLUE PIGMENT IN CORAL AND OTHER ANIMAL ORGANISMS. 267 



bands in the spectrum, one in the red and the other in the green ; 

 also that it is unaffected by dilute acetic, hydrochloric and sulphuric 

 acids, while dilute potash intensifies it. 



He also speaks in the same paper 1 of the blue pigment of Velella, 

 as being probably identical with that of other oceanic hydrozoa ; 

 no detached bands are exhibited, but the red and violet ends of 

 the spectrum are cut off. 



Fish. — Geo. Francis, (Adelaide) describes a bluish-green colour- 

 ing matter from certain species of Odax common in St. Vincent's 

 Gulf, S. A., giving a spectrum somewhat resembling that of chloro- 

 phyll. 2 The pigment is soluble in water, rather bluer than 

 chlorophyll ; sulphuric acid precipitates it with albumen, but does 

 not destroy the colour; it is bleached by light. The pigment is 

 nitrogenous, and is destroyed by heat, chlorine, acetic acid, alkalis, 

 ammonia, and alcohol. 



Turacin? — A blue pigment from the feathers of the turacoa or 

 plantain-eater, it is soluble in water and contains copper. 



Indigo — Although essentially a vegetable production, it was 

 specially tested for, since an indigo-forming substance occurs in 

 both normal and morbid urine. 4 But no certain indications of 

 the presence of indigo were obtained from the coral pigment. 



Pyocyanin. — Formed occasionally in pus. It forms blue acicular 

 crystals arranged in crosses or rosettes. Melts on heating and 

 does not sublime. Soluble in water ; reddened by acids, but the 

 colour is restored by alkalis. Neither the alcoholic nor the aque- 

 ous solution is precipitated by alum or lead acetate. 5 



Hcemocyanin. — This is present in the blood of certain cephalo- 

 pods, gasteropods, Crustacea and arachnida, and plays the same 



1 Quart. Journ. Micro. Science, 1873, p. 142 , and Journ. of Anatomy 

 and Physiology, Vol. iv. 



2 For figure and description see "Nature," Dec. 30, 1875, p. 167. 



3 A. H. Church— Phil. Trans. Roy. Soc, 1869, p. 627. 



4 For authorities see G-melin, Yol. xviii., p. 407- 



5 Gmelin, xviii., p. 415. 



