GREEN PIGMENT OF INTESTINAL WALL OF CHJETOPTERUS. 463 



scopic observations seem to prove conclusively that the green 

 pigment present in the blood is not chlorophyll. In order to 

 prove that it is a direct derivative of the chlorophyll taken in 

 with food into the alimentary canal, it seems to be necessary 

 to study the derivatives of chlorophyll, and to show that by 

 chemical processes a substance can be produced from chloro- 

 phyll having the absorption spectrum of Poulton's metachloro- 

 phyll, which it has not ; having the power of resisting the 

 destructive action of light, which it has not ; capable of diffusing 

 through a living membrane, and of existing in solution in an 

 acid albuminous fluid, which it is not ; and lastly of changing 

 to an opaque blackish brown pigment when simply exposed to 

 oxygen gas, which it is not. 



II. Description of Ch^topterin : its Mode of Occur- 

 rence AND Optical Properties. 



Mode of Occurrence. — Dr. Blaxland Benham has kindly 

 furnished me with an account of the mode of occurrence of the 

 intestinal pigment of Chsetopterus variopedatus from 

 observations made by him at my suggestion in Mr. Hornell's 

 laboratory in Jersey in the summer of 1896, and on material 

 preserved by him in formol and brought to Oxford. The 

 drawings in Plate 34 are by Dr. Benham, who has also recorded 

 the spectra of Chsetopterin and has carried out similar observa- 

 tions on Bonellin in my laboratory at Oxford. I am greatly 

 indebted to him for his assistance in preparing this account of 

 the two pigments. 



The body of this strange-looking Chsetopod is divided into 

 three regions, as shown in fig. 1. The dark green, almost 

 black-looking pigment is confined to the intestinal epithelium 

 of the middle region. It gives the whole of the inner surface 

 a black appearance, and can be seen through the transparent 

 tissues of the body-wall. 



In a transverse section its disposition is seen to coincide 

 with that of the entire epithelial layer of the intestine, as 

 shown in fig. 2. In order to observe satisfactorily its natural 



