ON CERTAIN GEEEN PIGMENTS IN INVERTEBRATES. 417 



points. Dr. MacMunn has shown that saponification with caustic 

 soda or potash is ineflPective, precipitation with acetate of lead is 

 better, for the yellow pigment remains in the solution. Traces 

 of it are, however, always liable to be carried down with the 

 enterochlorophyll, and the difficulty of re-obtaining unaltered 

 enterochlorophyll from the precipitate greatly diminishes the 

 utility of the method. The most useful method is, perhaps, 

 to add excess of acid, and shake with ether several times, then, 

 rejecting the ether, add alkali to the acid solution in too small 

 amount to neutralise the solution, and shake again with ether. 

 The ether takes up almost pure enterochlorophyll, which after 

 careful washing may be used for further experiments. The 

 method is, of course, wasteful, and not entirely effective, and 

 it is better, when possible, to obtain a solution from the fseces 

 where the yellow pigment is virtually absent. The purification 

 of enterochlorophyll from fats, and the other impurities with 

 which it is associated, is a matter of great difficulty. 



(4) Action of Acids. 



Enterochlorophyll resemble chaetopterin so closely that it is 

 not necessary to do more than note its characters, referring to 

 the description of chsetopterin for details. 



The bands shown by a solution of enterochlorophyll differ 

 slightly from those of chsetopterin, but the difference is not 

 marked. A neutral solution shows the following bands : 

 I X 667, II X 604, III X 539, IV X 503 (fig. 6). 

 If acid is added to a solution containing little lipochrome a 

 bluish colour develops, and the solution becomes five-banded 

 with the bands as follows : 



I X 657, II X 599, III X 567, IV X 534, V X 500. 

 This is the "enterochlorophyll" spectrum so frequently 

 fi'^ured by Dr. MacMunn. The fifth band, as in the case of 

 chaetopterin, tends to be indistinct. On further addition of 

 acid the solution turns green, the right-hand bands tend to 

 disappear, and the band in the red shifts back to its original 

 position at about X 667, just as occurs in the case of chseto- 



