ON CERTAIN GREEN PIGMENTS IN INVERTEBRATES. 409 



insoluble residue, the nitrogen does or does not enter into the 

 composition of the green pigment, or whether it is all con- 

 tained in the brown substance. 



Summary. 



The pigment chsetopterin dissolves readily in cold methy- 

 lated spirit or in ether to form solutions, which are indefinite 

 in colour, strongly fluorescent, and which give a spectrum 

 consisting of four distinct bands and a shading. 



When acid is added to the solution in methylated spirit, it 

 becomes first blue and then green. 



The blue solution is fluorescent, and distinguished by certain 

 peculiarities of the spectrum, but the fact that it can be made 

 to yield only original chsetopterin and a single-banded green 

 derivative seems to prove that its peculiarities are not in 

 themselves diagnostic of the existence of an acid derivative 

 comparable to Krukenberg's bonellidin, but are due to the 

 combination of the two pigments present. 



The green acid solution shows little fluorescence, and yields 

 similarly a mixture of chsetopterin and the one-banded acid 

 derivative. 



This acid derivative is characterised by its single faint band, 

 its green colour, and the absence of fluorescence. It is appa- 

 rently formed by the splitting of chsetopterin into an insoluble 

 brown residue and this derivative. 



Dilute alkalies have a twofold action upon chsetopterin. 

 They in part precipitate it as a compound insoluble in alcohol, 

 ether, and water, and in part convert it into a green derivative. 

 This derivative is characterised by its colour, its spectrum 

 consisting of two bands in the red, and its solubility in water. 



Salts of the metals, such as lead acetate, precipitate chseto- 

 pterin from its solutions, forming compounds which are in- 

 soluble in water, alcohol, or ether. By the action of dilute 

 acid on these compounds chsetopterin can be regenerated, but 

 it is liable to be intermixed with the acid derivative. 

 Chsetopterin, like bonellin, contains nitrogen. 

 The points which seem to me of special importance are that 



VOL. 41, PART 3. NEW SER. F F 



