in Plant Cytology. 193 
This, I think, is a mistaken view. Both exhibit an equal 
degree of plasticity. 
With the evidence now before us, I would suggest that 
every cell consists of the general protoplasm and of the nucleo- 
plasm, these together constituting the vegetative substance of 
the cell, while the linin and chromatin or chromosome sub- 
stance constitute the hereditary substance of the cell. Inmany 
cells the latter is chiefly aggregated in the nucleolus during 
the resting phase. From the nucleolus threads radiate out 
through the nuclear area and fuse to form the nuclear mem- 
brane, while from it radiating prolongations traverse the proto- 
plasm. Whether such threads are continuous from cell to 
cell through pores in the common walls is a question still 
needing solution. 
The Endonucleolus—At a time when the nucleolus was 
regarded as of small moment, I noticed as a uniform feature 
within it, in embryonic cells, a small clear body which was 
named the endonucleolus. Its constant presence in a wide 
range of tissues warranted me in regarding it as an element 
of possible importance in cell life. In recent years it has 
generally been spoken of as the nucleolar vacuole, and has 
been viewed as an inconstant factor. Meunier’s statement that 
it is absent in living cells of Spirogyra is unquestionably 
erroneous, though owing to the great density of the nucleolus 
it is frequently difficult of detection. If we are content to 
call it a vacuole, this will depend on the meaning which may 
attach tothe term. That it is often overlooked in embryonic 
tissues is to be explained by the overstained state of prepara- 
tions. I would still insist on its general occurrence and 
probable importance in living cells. Montgomery (p. 508) 
says: ‘In opposition to Meunier, and in agreement with most 
investigators, I must conclude that vacuoles are normal struc- 
tures in nucleoli, since they may be seen after the most 
diverse methods of fixation, and their size and number are 
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