CHAPTER IV 
THE COLOURS OF PROTOZOA, SPONGES, AND 
CCELENTERA 
Pigments of the Protozoa, their Characters, Variations, and 
probable Origin—Coloration of Sponges and Coelentera 
-—Distribution of Colours—The Colours of Corals and 
Sea-Anemones—Colour-resemblances in the Ccelentera 
—The Effect of Light upon the Development of Pigment 
—The Pigments of the Ccelentera—Optical Colours. 
The pigments of the Protozoa are mostly very plant¬ 
like, chlorophyll and lipochromes being exceedingly 
common. There is often an interesting alternation 
between chlorophyll and red or yellow lipochrome 
pigments, very similar to that seen in the vegetative 
organs of the higher plants. Thus Hcematococcus 
is sometimes red and sometimes green : it is always 
red in the resting stage, and gradually acquires the 
power of movement and a green colour simultaneously. 
Sometimes in this form and in Euglena there is 
merely a red ring round the nucleus ; when the 
green colour develops it begins at the periphery 
and gradually spreads inwards. Rostafinski found 
that the red colour is produced by a combination of 
two lipochromes, distinguished by their solubilities, 
