( 701 ) 
a feeble tannin reaction with ferric chloride. It does not result from 
this observation what is the fate of the tannin, but when the conju¬ 
gation is followed in greater detail, it is found that there is good 
ground for supposing, that at least a portion of the tannin serves as 
plastic material for the cell wall. Conjugation is a process which 
proceeds in such a way as to allow us to expect that its study 
in connexion with the point of investigation referred to will furnish 
us with important data, for conjugation does not start simultane¬ 
ously in all cells. Some cells are in advance of others; in a smaller 
or larger number of cells there is evidently a tendency to conjugate, 
but the conjugation does not succeed, and other cells again do not 
show a trace of the conjugation process. Whereas the conjugating 
cells form much reserve material as starch and fat, those which do 
not conjugate are apparently very poor in contents and they finally 
perish. The above mentioned differences seem to be determined by 
accidental circumstances such - as the coming into touch with cells 
of other filaments, the proximity of such cells and the position of 
the cells with regard to each other. They may even be observed 
with material which before conjugation consists exclusively of 
healthy normal cells. 
The point of interest in connexion with the tannin problem is 
the possibility of comparing, in conjugating Spirogyra filaments, cells 
which a short time before were quite equal and afterwards show 
more or less important differences, induced by accidental and rather 
superficial circumstances. It is of interest to trace in these various 
cells what happens to the tannin content. This was investigated with 
the caffeine- and antipyrine solutions I have recommended, and it 
was striking to note, how differences in the development of the cell 
wall corresponded to the quantity of tannin present in the cells. 
Thus I could ascertain, that in cells where the lateral protrusion 
and mutual fusion had taken place, the tannin content was always 
appreciably smaller than in cells which only showed the first 
beginnings of the lateral protrusion. These two kinds of cells only 
differed as regards cell wall and tannin content; for the rest they 
still agreed perfectly. They were distributed promiscuously over the 
filaments, as is usual in conjugation. The'se facts seem to me to prove 
that there is a connexion between formation of the cell wail and 
the tannin content, and the supposition, that tannin serves as plastic 
material for the cell wall is very plausible. 
Furthermore there is a remarkable increase in the tannin content 
of those cells which have not had an opportunity of conjugating or 
in which the process was interrupted at an early stage; these cells 
