379 
A Iga-like Organism. 
inclined to be oblong in shape, from i 2-20 /x long and 6-9 /x 
wide. It is differentiated into a nucleus, two spaces con- 
taining cell-sap, a chromatophore and a pigment-spot, which 
will now be described in turn. 
The nucleus may readily be distinguished from the other 
structures of the cell without special treatment. It is situated 
very nearly in the centre of the cell and is held in position 
by a band of protoplasm that completely fills up that portion 
of the cell which lies between the nucleus and the sides of the 
wall. From this band of protoplasm, that surrounds and 
encloses the nucleus, a layer of protoplasm extends around 
the ends of the cell, on the periphery, so as to enclose two 
spaces containing cell-sap, one above and the other below the 
nucleus, as the position of the cells is normally upright. 
The very large chromatophore is embedded in the peri- 
pheral layer of protoplasm. It extends as a band completely 
around the middle portion of the cell and usually entirely 
around the ends, but the latter, and particularly the upper 
end, are sometimes hyaline. 
The cell therefore usually appears of a uniform green 
colour, but the shade is darker or lighter in different parts of 
the cell, depending upon the relative thickness of the chro- 
matophore in those portions. There are no pyrenoids, and 
the small starch-grains embedded in the chromatophore are 
not, as far as the writer could see, arranged around any 
amylum-centres. 
The bright red pigment-spot lies in the chromatophore 
usually about a third the length of the cell from the inferior 
end. It is very variable in size, in some cells being scarcely 
visible, in others very large. It reaches its greatest develop- 
ment in the motile stage of the plant, to be described later, 
where it is sometimes 1 J /x in diameter : and, when it is 
as large as this, a distinct granulated structure is often 
apparent. 
The reader will have noticed the processes extending from 
the inferior end of the cell in Fig. 2, and also that there 
is often a space between the mass of protoplasm and the 
D d 2 
