II 
THE PIGMENTS OF ORGANISMS 
43 
Looking at the distribution of blue pigments 
more in detail, we find that while blue and purple 
colours are common in the Flowering Plants, there 
is much uniformity in the pigments, which seem all 
to belong to the anthocyan series. In the lower 
plants blue pigments are more numerous. Thus 
various blue and purple pigments have been described 
among Bacteria—the blue or purple colour which 
develops on decaying meat is a good example. 
These pigments have been compared by some to 
natural aniline dyes. With these, and as yet of little 
interest except to the chemist, we may put the 
bluish-green colours of certain Fungi. 
A more interesting pigment is phycocyan, which 
occurs in the bluish-green Algse (Cyanophycese). It 
is a beautiful pigment, blue in transmitted and blood- 
red in reflected light, and is said by Molisch to be of 
albuminoid nature. It is soluble in water, and has 
been obtained in crystalline condition. 
In animals blue pigments seem to be more 
numerous than in plants. They are found in various 
Protozoa, as in Nassula and Stentor; in the former 
it seems possible that the pigment is taken up from 
the blue-green Algae of the food. In the Coelentera 
blue pigments are exceedingly common, especially 
in shallow-water forms in warm seas, and in the 
pelagic jelly-fish. In worms and in Echinoderms 
we find that, although blue colours occur, the pig¬ 
ments producing them do not appear to have been 
isolated. Similarly in insects, where blue is very 
common, blue pigments have not yet been described, 
although it is improbable that the blue in all cases 
is structural. 
