344 C. A. MACMnNN. 



adding caustic potash solution the reddish-brown colour is 

 restored. 



Weak spirit will not dissolve the pigment, as Moseley 

 found it did in the case of Polyopogon amadou.^ 



Hence it is quite evident that the pigment is quite dif- 

 ferent from Spongioporphyrin. 



III. The Pigment of a Gorgonian Coral, Pterogorgia pinnata. 



Professor Lanhester found the pigment of this species 

 "■ insoluble," and truly it is so. I tried all kinds of solvents, 

 but without result. Alcohol, ether, chloroform, acidulated 

 water, aqueous alkaline solutions, etc., were all tried in vain. 

 In the case of the Alcj^onarian Heliopora Moseley ^ found 

 he could get the pigment out by dissolving the corallum in 

 hydrochloric acid. I tried all kinds of acids, but with a 

 negative result. The pigment as it is present in the or- 

 ganism does not seem affected by acids or by alkalies. I 

 may mention that the spirit in which this specimen had been 

 preserved showed a faint chlorophyll spectrum. 



From a specimen of the solid pigmeut mounted in balsam, 

 which Professor Lankester had prepared, I could see no 

 definable bands with the microspectroscope, so that one can 

 infer that this pigment is not related to Spongioporphyrin, 

 and it is not identical or apparently related to the pigment of 

 Polyopogon. 



Remarks, — On looking up the literature of sponge pig- 

 ments I cannot find any mention of any pigment which 

 presents the characters of Spongioporphyrin. 



Krakenburg^ is the only observer who has made any 

 extended observations on the pigments of sponges. I 

 thought at first I was dealing with a '^ floridine " when 



> ' Quuit. Journ. Micr. Sci.,' vol. xvii, N. S., p. 1. 



2 'Vergl. jjliyMol. Vortriige/ 1S8G, ill, aud ' Vergl. plijsiol. Stud.,' 1882, 

 p|). 22, etc. 



^ For rlili)ropl:\ n, etc., 'ii spoiif^^cs, see ' Joiirn. Pliysiol.,' vol. ix, No. 1. 



