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diluteoleine. On still further exposure to the air a red 
colouring matter is formed, which may be distinguished by 
the name of Aphidirhodeine ; but this may be more conve- 
niently obtained pure in the manner described in the sequel. 
As in the case of all such substances, their spectra are best 
seen when they are dissolved in bisulphide of carbon, for 
then the absorption-bands lie farther from the blue end, and 
there is no chance of there being any variation in their 
position, owing to any difference in the amount of water that 
may be present in alcohol or ether. When carefully picked 
out living Aphides are crushed up in a test tube with the 
bisulphide, the colour is at first red, but almost immediately 
changes to yellow; and on stirring them up so as to expose 
to the air and to the bisulphide, the original Aphideine is 
rapidly altered into Aphidiluteine, which dissolves in the 
liquid, giving a bright yellow solution. This should be 
filtered and examined at once. The spectrum of transmitted 
light shows two well-marked absorption-bands in the blue, 
situated much nearer to the extreme blue than those of any 
other analogous substance which has come under my notice. 
It is alse very fluorescent, of a fine green colour, and this 
light of fluorescence gives the spectrum shown in No. 4 of 
the following woodcut, fig. 2: 
Fig. 2.—Spectra of the Light of Fluorescence. 
Red end. Blue end. 
4. Aphidiluteine. 
5. Aphidiluteoleine. 
6. Aphidirhodeine. 
D F Fraunhofer’s lines. 
The whole of the green part of the spectrum is seen, with 
the exception of two somewhat faint bands, which I believe 
are due to the Aphidiluteine itself, but am not quite certain, 
since it rapidly changes into other compounds which have 
absorption-bands nearly in the same situation. On keeping 
the above-named solution for some hours it is completely 
