ON COLOURING MATTER OF BONELLIA VIRIDIS. 169 
might at all events be looked upon asa chlorophyll sub- 
stance ; but when more carefully examined it is soon found 
to differ completely from either blue or yellow chlorophyll 
or chlorofucine, which, according to my views, are the only 
genuine species of the genus chlorophyll hitherto described.! 
All of these are changed by strong acids into new substances, 
so that when the solution is subsequently neutralized the 
spectra are found to be totally unlike those of the original 
substances. On the contrary, on adding an acid to the green 
alcoholic solution of bonelleine the colour becomes purple, 
there is a great change in the spectrum, due to the removal 
of some bands and the greater development of others, but no 
other alteration, even after many days, and on neutralizing 
. the acid the original spectrum is again seen just as at first, 
thus proving that no such decomposition takes place as in 
the case of chlorophyll. In this respect it resembles the 
well-known product of the action of acids on blue chlorophyll, 
but this latter differs from bonelleine in giving the same 
spectrum when the solution is acid as when it is neutral or 
alkaline. 
Bonelleine also differs from the three different species of 
the chlorophyll group in the character of its fluorescence. 
The neutral alcoholic solution gives éwo bright bands, whose 
centres aré€ at wave-lengths 643 and 588, whereas the 
chlorophylls give only one. The spectrum of the fluores- 
cence of the acid solution of bonelleine gives a single bright 
band at wave-length 619, whereas that of the product of 
the decomposition of blue chlorophyll by acids gives two. 
These are such important differences that it seems desirable 
to look upon them as of generic value, though, at the same 
time, in the present state of our knowledge it would, perhaps, 
be premature to decice what characters should be considered 
sufficient to constitute a natural group, or, so to say, genus, 
of colouring matters. 
Before describing the various spectra in the manner already 
explained, it would be well to give the wave-lengths of some 
of the principal Fraunhofer lines, so that the position of the 
absorption-bands may be better understood by those who 
have been in the habit of referring their observations to those 
lines : 
A 760 B_ 686 C 656 D 589 
KE 527 G Ori F 486 G 430 
The greatest number of bands that I have seen in any 
1 «Proceedings of the Royal Society,’ vol. xxi, p. 452. 
