diteh-water all the cells perished in one day. In sotution of 1 part 
in 500.000 parts of ditchwater or Kwnopp’s fluid many dead cells 
were seen after one day and in a solution prepared with distilled 
water of the same strength the number of dead cells was still 
greater. No growth was observed. The poisonous action of methy- 
lene-blue is the reason why there can be no question of “Kontrole 
des jeweiligen Zustandes des Zellsaftes und der Veränderungen 
dieses im Laufe der Entwicklung’, as Prrrrer imagines. 
It has been already demoustrated above that the cell-sap of Spiro- 
gyra contains no dissolved protein. The precipitate with methylene- 
blue cannot therefore as Prurrer believes, contain protein. In his 
opinion the precipitate is actually a compound of tannin with me- 
thylene-blue, which cannot be brought into agreement with the fact 
that solutions of methylene-blue, even stronger than those used by 
Prrerrer remain clear with solutions of gallnut- and Spirogyra-tannin. 
This is not explained by Prrrrer. 
It is noteworthy that when Spirogyra is placed in a dilute methy- 
lene-blue solution (J in 500.000) there is no gradual formation of a 
precipitate which is coloured blue from the beginning, but there is 
first a colourless or almost colourless precipitate and that this is 
then gradually coloured a deeper and deeper blue. Of this Prerrer 
makes no mention. 
On examination of the precipitate with reagents tannin reactions 
could be obtained, for example, the black coloration with ferric 
acetate. It may therefore be assumed that tannin is precipitated. The 
quantity of the precipilate even in Spirogyras with much tannin 
was however, small compared with other tannin precipitates. 
Hence I doubted whether the tannin is completely precipitated. 
After one day I could not, indeed, demonstrate any tannin in the 
cell-sap in addition to the precipitate, but it seems that the cells may 
lose tannin by exosmosis, For when, for example, pieces of Spiro- 
gyra-filaments were placed in a dilute solution of methylene-blue, 
containing */,°/, gelatin, a precipitate was formed outside the cells 
and between the layers of the cell-wall which separated from each 
other. The precipitate was a compound of gelatin with tannin and 
became coloured black with ferric acetate. I cannot therefore venture to 
assume with Prerrer, that a complete precipitation of tannin takes 
place in the cell-sap. 
It seems to me that various factors play their part in the pro- 
duction of the precipitate. In the first place the harmful action of 
the methylene-blue, of causing great modifications in the organism. 
Further the presence of salts appear to assist the formation of pre- 
