ON CERTAIN GREEN PIGMENTS IN INVERTEBRATES. 407 



the presence of the derivative in such solutions is only 

 indicated by the appearance of a new band at X 625, and 

 sufficient unaltered chsetopterin remains for the solution to 

 retain its fluorescence and its original four bands in addition 

 to the new one. The point is emphasised because it seems to 

 have some bearing upon the characters of bonellin. When 

 the ammonia derivative is formed by heating chsetopterin with 

 ammonia, the band at X 625 is often difficult to demonstrate. 



(b) Caustic Soda and Potash. — Very dilute solutions of 

 these when added to the alcoholic solution produce the same 

 effect as ammonia, — that is, there is a slight green insoluble pre- 

 cipitate, and the solution remains pure green, showing two 

 bands in the red, one at X 661 and one at X 625, witli more or 

 less distinct traces of other bands, and yields a pigment which 

 is readily soluble in water or dilute alkali. If a considerable 

 amount of caustic soda or potash be added, however, the 

 solution turns dull yellowish brown, and when shaken with 

 ether, the ether removes a yellow pigment which gives a faint 

 band at X 661, the band of chsetopterin. This pigment seems 

 to me to be a product of decomposition, showing that 

 chsetopterin is destroyed by strong alkali; a mere trace of 

 unaltered chsetopterin would be sufficient to yield the band. 



It thus appears that dilute alkalies have a double eflfect upon 

 chsetopterin. In the first place, the pigment forms with 

 alkalies a compound of green colour which is insoluble in 

 water, alcohol, and ether, and from which original chsetopterin 

 can be recovered by the action of acid. In the second place, 

 alkalies give rise to an alkaline derivative of green colour, 

 which is soluble in water as well as in dilute alkali and alcohol. 

 Solutions of this in alcohol are not fluorescent, and show two 

 bands, one at X 650 and the other at X 625. 



(4) Action of Salts. 

 The addition of salts like lead acetate or copper acetate or 

 sulphate to alcoholic solutions of chsetopterin causes a precipi- 

 tation of pigment. In the case of lead acetate the precipi- 

 tated pigment is bright yellow-green in colour, and is insoluble 



