290 Phillips on a Comparative Study of the 
Cohn (16) discussed at some length the coloring material 
of the Cyanophycez, but did not deal with the question of 
the chromatophore. He found a green coloring substance 
which was soluble in alcohol, and which he considered to be 
chlorophyll, and a blue pigment which he termed phycocya- 
nin which was soluble in water. Naegeli had termed the 
light green pigment phycochrome, and when the bluish 
tint was present he called it phycocyan, this latter being 
synonymous with the phycocyan of Kutzing. Evidently 
therefore the phycocyan of Nageli was a compound of the 
two pigments mentioned by Cohn, and the name phycocyan 
should properly belong to the simpler substance as applied 
by Cohn. A third pigment, phycoxanthin, was met with 
by the latter observer in those forms of the Cyanophycez 
which have the purple color. This he found to be a modi- 
fication of the phycocyan, differing very little from the blue 
variety. Hansgirg found that the pigments of the Cyano- 
phycez had the power to elaborate food without the pres- 
ence of light, but whether this was due to the phycocyan, 
he does not say. Certainly it cannot be due to the chloro- 
phyll alone. It would be of interest to know if the recently 
discovered Roentgen rays, or any similar cause, could be 
active upon the chlorophyll when the phycocyan is present. 
Molisch (55) demonstrated that the phycocyan was a crys- 
talline albuminous body, easily recognizable in plants fixed 
in a solution of cupric sulphate. Warming (80) considered 
that there was no chromatophore except possibly in a few 
forms such as Glaucocystis where it might be slightly devel- 
oped. Zacharias could not determine its presence because 
he could not see a bounding membrane. Crato (19) found 
a sharply defined chromatophore, having an amoeboid-like 
form, and with thick stratification. Zukal (103) thought 
that a highly organized chromatophore was usually lacking, 
though he was able to determine a thin utricle-like layer of 
clear protoplasm between the colored crust and the cell wall. 
Nadson (57) considered the whole colored protoplasmic 
