424 MARION I. NEWBIGIN. 



of colour and indefiniteness of bands, reappear; when it is 

 known that bonellin normally occurs in the alkaline state it is 

 difficult not to regard tbis fact as an additional proof of affinity. 

 As to the additional band at X 550 in bonellin, it is to be re- 

 collected that it is very faint, so faint that it was missed by 

 Sorby (11) entirely; I believe that it is the same band as that 

 described at A 545 in acidified solutions. It will be recollected 

 that in solutions of chsetopterin a similar band occurs, which 

 is only distinct in acidified solutions, but is represented in 

 normal ones by a faint shadow. 



It may be well to summarise briefly these facts. 



1. Neutral solutions of chsetopterin and of bonellin re- 

 semble one another in their indefiniteness of tint, in their 

 strong fluorescence, and in possessing a spectrum of four bands 

 occupying similar but not identical positions. Chsetopterin 

 solutions show, in addition, a faint shadow in the green, not 

 yet described in neutral bonellin solutions. A similar band, 

 however, occurs in normal (alkaline) solutions of bonellin. 



2. The addition of a little acid turns chsetopterin solu- 

 tions blue, bonellin solutions violet, without diminution of the 

 fluorescence. The spectrum is considerably altered, but the 

 alteration in the two cases is similar in so far as in each a new 

 band appears or becomes distinct, and the fourth band of the 

 original spectrum tends to grow faint or disappear. The most 

 striking diff'erence is seen in the fact that in chsetopterin the 

 position of the red band only alters slightly, in bonellin it 

 alters much ; but the difficulty is diminished by the fact that 

 the acid cheetopterin solution can be proved to possess a band 

 analogous to that of acid bonellin, which is concealed by the 

 presence of the original band in the red. Further addition 

 of acid in both cases produces a further change of colour, and 

 the reappearance of the original band in the red. 



3. Normal (alkaline) bonellin and chaetopterin which has 

 stood with alkali resemble one another in their deep green 

 colour and fluorescence, and in showing the four-banded 

 spectrum of the neutral form, plus an additional faint band in 

 the red. They differ from one another in that bonellin shows 



