GREEN PIGMENT OF INTESTINAL WALL OF t'UiiTOPTEltUS 45o 



An extremely interesting comparison suggests itself with the 

 " entero-chloropliyll^' described by Dr. MacMunn as occurring 

 in corpuscles in the livers (gastric glands) of Mollusca and 

 in other Invertebrata ('Proc. Roy. Soc./ vol. xxxv, p. 370). Dr. 

 MacMunn was probably ill-advised in using the term ''chlo- 

 rophyll^' in connection with the substance discovered by him. 

 I have no doubt that he was led by my own erroneous classifi- 

 cation^ of several green pigments in animals under the chloro- 

 phyll group. It is not possible to come to a conclusion from a 

 comparison of the absorption spectrum assigned by Dr. Mac- 

 Munn to his entero-chlorophyll with that of Chsetopterin, since 

 Dr. MacMunn's pigment is very difficult to obtain free from 

 admixture with other substances. On the other hand, Chseto- 

 pterin can be obtained in a fairly pure condition, so far as the 

 admixture of other pigments is concerned, by isolating the 

 mid-region of the body of Chaetopterus and preparing the 

 alcoholic solution from that region only. It is true that even 

 so the solution contains fatty matters and other impurities, 

 and that we have not yet obtained Chsetopterin either as a 

 pure thoroughly cleansed powder or in the crystalline con- 

 dition. 



An investigation of the chemical properties of Chsetopterin 

 has been undertaken at my request by Miss Newbigin in 

 Professor Noel Paton's laboratory, and there is reason to hope 

 that before long we shall obtain this body in a chemically pure 

 state, and learn something as to its chemical constitution and 

 properties, which cannot fail to throw light on its physiological 

 significance and possible relationship to MacMunn's entero- 

 chlorophyll. 



The determination of the characters of a body occurring in 

 such definite form in the enteric epithelium of one of the 

 simpler forms of animal life cannot but lead to a better under- 

 standing of the physiology of the alimentary canal, and of the 



' This error of course did not include the green pigments of Spongilla, 

 Hydra, and such ciliate Protozoa as Stentor. In them tliere is no doubt that 

 the green pigment is chlorophyll, and that it occurs, as in plants, in selt- 

 propagating corpuscles. 



