ON CERTAIN GREEN PIGMENTS IN INVERTEBRATES. 423 



already seen that the apparent single band of the latter is in 

 reality formed by the apposition of two bands^ of which the 

 second has its centre about X641, It is^ as I think^ this band 

 which corresponds to the first band of acid bonellin. In other 

 respects there is, as already seen, considerable analogy between 

 the two sets of spectra. Thus the band at X 545 in acidified 

 bonellin obviously corresponds to the band at X 560 in acidified 

 chsetopterin ; the disappearance of the violet band of neutral 

 bonellin is paralleled by the dimness of the corresponding band 

 in the case of chaetopterin. On the fact that the yellow and 

 green bands of chaetopterin change little on the addition of 

 acid, while those of bonellin show considerable movement, I 

 am not inclined to lay any stress. My own observations 

 showed considerable discrepancy from those of Engelmann on 

 this subject, and I am strongly of opinion that the movement 

 varies with the amount of acid in the solution. 



The most apparent difference from chaetopterin which 

 bonellin shows is in the characters of its alkaline solution. 

 Professor Lankester has made the exceedingly interesting dis- 

 covery that normal bonellin is alkaline, — that is, that the 

 pigment apparently occurs in the animal in the alkaline 

 condition. This alkaline solution gives no less than six bands, 

 of which four are those of neutral bonellin, while the other 

 two have their maximum points of absorption at X 614 and 

 X 551 respectively. The solution is bright pure green, with 

 strong fluorescence. Now we have already seen that when 

 chaetopterin stands for some time with alkali it becomes pure 

 rich green with undiminished fluorescence, and then shows a 

 five-banded spectrum (fig. 4) with two bands in the red, the 

 original one and a new one at X 625 ; at the same time the 

 bands in the yellow and green show a marked diminution. 

 When one passes from the study of normal chaetopterin to 

 that of normal (alkaline) bonellin, the most striking differences 

 are, in the latter case, the definiteness of the colour and the 

 indistinctness of the bands, except that in the red and to a 

 less degree that in the violet. In working at the action of 

 alkalies on chaetopterin these same characteristics, definiteness 



