Hazen: Lire History OF SPHAERELLA LACUSTRIS 281 
spectrum, and only a feeble darkening in the position of the char- 
acteristic chlorophyl band between P and C; while the more the 
cells changed from red to green, the stronger was the absorption 
between P2 and C, and the feebler that in the yellow and green. 
Engelmann's experiments therefore quite justified his conclusion 
that the photosynthesis in the red cells of Haematococcus is due not 
to the red color but to the presence of chlorophyl mixed with it. 
The experiments of Engelmann with living cells have been 
confirmed by Zopf's researches on the extracted coloring matters. 
Zopf ('95) collected about a kilo of red Haematococcus and ex- 
tracted the coloring substances with warm absolute alcohol. 
From this alcoholic solution he separated* a chlorophyl solution, 
a yellow pigment solution, and a red pigment solution. Zopf also 
extracted the so-called haematochrom of Trentepohlia but found 
that it formed a yellow solution similar to the yellow solution from 
Haematococcus if not identical with it. This yellow pigment, or 
carotin, is to be sharply distinguished from the red pigment; it 
constitutes only a small element in the coloring matters of the 
red cells of Sphaerella. The red pigment forms a brick- to blood- 
red colored combination with alkalies and alkaline earths ; the so- 
lution in alcohol, ether, and petroleum-ether, as well as the evap- 
oration residue, shows the same red tint; and the spectrum gives 
a single but broad absorption band in the green and blue, 
strongest in the line 7; The yellow carotin of Trentepohlia, on 
the other hand, forms no combination with alkalies and alkaline 
earths ; the extracts in alcohol, ether, and petroleum-ether as well 
as the evaporation residue are yellow ; and the spectrum shows two 
narrow absorption bands in the blue and indigo. 
Zopf thus shows that the assumption by Cohn ('67) and Ros- 
tafinski ('81) that the reddish pigment of Trentepohlia and the haema- 
tochrom of Haematococcus are identical was not warranted by facts. 
He considers the yellow carotin one of the eucarotins, pigments 
which are carbohydrates : the red pigment, for which the name 
haemotochrom may still be used in the restricted sense, is a repre- 
The raw alcoholic mixture was treated with a solution of caustic soda and the 
fact that the chlorophyl-sodium is solub'e in water, the yellow pigment easily soluble 
in petroleum-ether and the red less soluble in petro'eum-ether. 
