METABOLISM 269 
condition is followed by the granular one, and in this state 
the cell can remain for some time before the enzyme is 
discharged. When this has happened the hyaline condition 
is resumed. 
The formation of the cell-wall which separates the cells 
is due to a similar activity of the protoplasm. The division 
of cells or the development of new protoplasts will be more 
fully considered in a subsequent chapter. It will suffice to 
say here that in all ordinary growing points this division 
of a protoplast into two is followed immediately by the 
formation of a new supporting membrane between 
them. 
The division of the cell is preceded by the division of 
its nucleus, which is attended by a series of complicated 
movements of particular constituents of its substance. The 
two daughter-nuclei are situated at some little distance from 
each other and are connected by a number of delicate fila- 
ments which are gathered to a point at each end and spread 
out in the centre, forming what is called the nuclear spindle. 
This generally stretches completely across the long diameter 
of the cell. 
During these introductory changes the hyaline proto- 
plasm becomes more granular, and the granules, technically 
spoken of as microsomata, are attracted to the spindle 
fibres. They pass along these fibrils from both regions of 
the cell and form a plate of extreme tenuity across it, 
midway between the two nuclei. This plate soon under- 
goes a transformation, the granules disappearing and the 
membrane becoming translucent, and so forming the ordinary 
substance of the cell-membrane, generally, though perhaps 
not strictly accurately, known as cellulose. The cell-wall 
is thus seen to be formed from the protoplasm, or to be 
secreted by it, the granules or microsomata of which it is 
at first composed being the result of decompositions set up 
in the living substance. 
When cell-walls are growing in thickness or in surface 
a similar decomposition of the protoplasm can be observed. 
