446 FREDERICK KEEBLE. 
the size of the whole cell; in others, two or even three such 
clear vacuole-like structures may occur. Moreover, instead 
of the occasional refractive globules, the yellow-brown cells of 
animals examined immediately after capture are found to 
contain, in many instances, large numbers of such globules | 
(Pl. 27, figs. 8 and 9). Not only are these globules to be 
observed in the yellow-brown cells, but they may be seen 
also lying in the animal tissue itself (Pl. 26, fig. 6). 
The numerous yellow-brown discs which make up the bulk 
of the cell contain two pigments—a yellow pigment and a green 
pigment having the appearance of chlorophyll. The green 
is masked by the yellow pigment, but may be demonstrated 
by treating the animal with 90 per cent. alcohol. Thus acted 
on, the yellow pigment screening the chlorophyll dissolves 
rapidly and discs become green. Similarly, hot water destroys 
the yellow and reveals the green pigment. In this respect 
the yellow colouring-matter behaves like Phycopheein, the 
pigment of the brown alge. When 90 per cent. alcohol is 
added to cells, the yellow pigment of which has been extracted 
by hot water, the green colour is intensified. The yellow 
pigment is only shghtly soluble in dilute alcohol. Acted on 
by concentrated sulphuric acid the cells take on a beautiful 
emerald-green colour. These reactions serve to distinguish 
between the yellow-brown cells and the orange glands. The 
pigment of the latter is removed by 90 per cent. alcohol, but 
when so removed leaves no green colour behind. Treated 
with concentrated sulphuric acid the orange pigment of the 
glands undergoes no change. 
There can be no doubt that the discs which make up so 
large a part of the yellow-brown cell and which give to it its 
distinctive colour are chloroplasts. The reason for the marked 
difference between the more central, polygonal, or oval, 
pale chloroplast, and the peripheral, elongated, boat-shaped, 
darker chloroplasts is not obvious. The contrast between 
the two kinds is so marked as to make it unlikely that the 
difference is merely optical—due to the latter presenting 
themselves in profile. It may be that the more peripheral 
