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extent towards the blue end, when ether is employed as the 
_ solvent. 
On agitating the solution of this Aphidirhodeine in ether 
with water containing a little ammonia, the greater part of 
the colour is deposited as a green layer between the water 
and the ether, as though the alkaline modification were in- 
soluble in both water and ether. Separating this and mixing 
it up in dilute alcohol it gives the spectrum No. 3 of fig. 1, 
and this fact led me to think it probable that the substance 
which gives these bands, formed on exposing a solution of 
aphidieine to the air, is really Aphidirhodeine remaining in 
a state of very unstable solution. I therefore added to such a 
preparation two or three times its bulk of alcohol, and on 
agitating with excess of bisulphide of carbon obtained a red 
solution of Aphidirhodeine with some Aphidiluteoleine. It 
therefore appears that though the products derived from 
Aphideine are not dissolved by water, they may in some 
cases remain in solution for a time, so as to give a more or 
less clear liquid. I specially mention this because as an 
almost universal rule colouring matters soluble in water are 
insoluble in bisulphide of carbon, or in fats and oils; and 
misled by the apparent solubility in water, it was some time 
before I discovered that this brown, dirty-looking solution was 
in great measure coloured by the clear red and highly fluo- 
rescent substance obtained as already described by the use of 
bisulphide of carbon, for on superficial examination they 
seem to have so very little in common. 
As already named, when the living insects are crushed up 
in ether, a small quantity of a yellow colour is obtained ana- 
logous to that in the fat or wax of other insects, but no 
Aphidiluteine, which, therefore, appears not to be a normal 
constituent. If the insects be killed by exposure for a short 
time to the vapour of bisulphide of carbon, and the colouring 
matter dissolved out by ether in the course of a few minutes, 
the amount of Aphidiluteine obtained is very small ; but, if 
the insects have been kept dead for a quarter of an hour, 
there is no difficulty whatever in proving that a considerable 
part of the Aphideine has changed into Aphidiluteine even 
in so short a period of time. After having been kept dead 
for about a day very little unaltered Aphideine remains. On 
keeping them much longer they turn darker and transmit 
red light, showing the absorption bands of Aphidirhodeine. 
These facts clearly prove that in such inquiries it is most 
important to decide whether the colouring matters are or are 
not present in the living insects. The change from Aphi- 
deine to Aphidiluteine is so rapid that I was for a consider- 
