ON CERTAIN GREEN PIGMENTS IN INVERTEBRATES. 413 



plasm, as described by Dr. MacMunnj coloured oil-drops 

 occur. Sections of the digestive gland are by no means easy 

 to cut when, as in the present instance, the ordinary harden- 

 ing agents are inadmissible. Many of the cells are ruptured 

 in the process, and mingled with the debris there occur green 

 oil-drops like those found mixed with the contents of the gut 

 in Chaetopterus. I am of opinion that these contain the 

 pigment enterochlorophyll, while the brownish vesicles pro- 

 bably contain it intermixed with yellow pigment, which may 

 also occur diffused through the protoplasm. The colour of the 

 liver varies greatly in different specimens, the differences being 

 apparently due to variations in the amount of enterochloro- 

 phyll present. The presence of the pigment in the cells of the 

 gut and in the faeces seems to me of prime importance from a 

 comparative point of view. 



(3) Characters of Solutions. 



In the earlier experiments great care was taken to diminish 

 the risk of contamination of the solutions by plant chlorophyll 

 from the gut. In the limpet portions of the liver were care- 

 fully dissected away from the coils of the gut and dropped into 

 methylated spirit. As it takes some thirty or forty limpets to 

 yield a very moderate amount of solution, the process is a 

 somewhat tedious one. It was found later that the risk of an 

 intermixture with plant chlorophyll is in reality very small if 

 care be taken to remove the "manyplies^^ and its contents, 

 for the digestive juices seem to very speedily destroy the 

 chlorophyll, and it rarely occurs in the small intestine. 

 After the discovery of the presence of the pigment in the 

 faeces was made these were employed as sources of the pig- 

 ment. The absence of lipochrome pigment and of fat in 

 solutions obtained from them greatly simplifies further opera- 

 tions. 



To obtain the pigment the parts employed, whether liver or 

 faeces, should be dried and powdered, and the powder extracted 

 with cold methylated spirit, in which the pigment is exceed- 



