ON CERTAIN GEEEN PIGMENTS IN INVERTEBRATES. 419 



on standing, which can hardly be described as a " reconversion." 

 When the pigment is actually converted into the one-banded 

 acid derivative it cannot be reconverted into the normal 

 pigment. The difference between chlorophyll and the pig- 

 ments enterochlorophyll and chsetopterin as to the action of 

 acids, is more accurately expressed by saying that the latter 

 are relatively insensitive to the action of acids, while the 

 former is exceedingly sensitive. 



Enterochlorophyll can be precipitated from acid solution by 

 the addition of marble, just as chsetopterin can. Solutions of 

 the former, however, when obtained from the liver and 

 intestine always contain fat and other impurities, which may 

 more or less disguise the reactions. 



(5) Other Reactions. 



In its other reactions also " enterochlorophyll " shows a 

 remarkable resemblance to chsetopterin. The action of 

 ammonia is to turn the pigment green, although the colour 

 may be concealed by the presence of the yellow pigment; to 

 alter its spectrum ; and to render it soluble in water. As to 

 the spectrum of this ammonia derivative, I have only been 

 able to find one band at about A 655, instead of the two of the 

 corresponding chsetopterin derivative ; but as the second band 

 is often difficult to demonstrate in the case of chsetopterin, I 

 am not disposed to lay much stress upon this fact. In regard 

 to it and to some other trifling differences from chsetopterin, 

 it seems only necessary to point out that not only does 

 enterochlorophyll occur in smaller amount than chsetopterin, 

 but also the solutions contain a large admixture of foreign 

 substances, which are of course increased in relative amount 

 with every increase in the strength of the solution. These 

 intermixed substances greatly increase the difl&culty of making 

 observations, especially in regard to solubilities and so forth. 



Enterochlorophyll is to some extent precipitated by ammonia 

 just as chsetopterin is. The addition of acetate of copper or 

 lead to a solution of enterochlorophyll causes a precipitation 



