come into contact. This takes place at one or more points on the 
circumference of the vesicle. At these points precipitates are produced, 
but it cannot be seen whether at first small openings or tears occur 
in the vesicle. It is often possible to distinguish two parts in the 
precipitates: the one is compact and seems to lie within the vesicle ; 
the other is looser and occurs outside the wall of the latter. 
When the precipitates are investigated with reagents, they are 
found to consist of protein and tannin. With sugar-solution and 
85'/,°/, sulphuric acid they become very distinctly red, especially 
the more compact portion; after treatment with iodine in potassium 
iodide solution and washing out with water they show a reddish 
violet colour. With ferric acetate they become blue-black, with 
potassium bichromate brownish-red. 
From these results [ think the following conclusions may be 
deduced. The vesicle contains a solution of protein, which is derived 
from the cytoplasm and probably occurs there in soluble condition 
in the alveolar fluid. When the protein-solution and the cell-sap 
containing tannin come into contact with each other, the above 
mentioned precipitates are formed, from which it follows, in my 
opinion, that in addition to tannin protein in solution cannot be 
present in the eell-sap. They would at onee form an insoluble 
compound with each other. It is thus impossible that, as Lorw and 
Bokorny assume, the precipitates, which are formed in the cell-sap 
by basic substances, are protein-precipitates or, as PFEFFER assumes, 
precipitates of protein and tannin. 
In reality they are tannin precipitates. Although the possibility 
is not excluded that other substances are sometimes present in 
small quantity, experimental investigation yields the proof, that there 
can be absolutely no thought of protein-substances in the first place. 
Tannin and protein are separated in the living cells in a 
remarkable manner. Tannin in solution occurs in the cell-sap ; 
proteins can be demonstrated in the nucleus, the chromatophores 
and the cytoplasm. They are either solid, as for example, the 
pyrenoids of the chromatophores or dissolved, as in the eytoplasm. 
The nucleoli whick contain a viscous substance, in which the two 
nucleolus-threads Jie ') give specially clear protein-reactions. 
There still remains the question why a solution of ammonium- 
carbonate which causes a precipitate in the cell-sap of Spirogyra, 
may be much more dilute than that which produces a precipitate 
in a solution of gallnut-tannin or of Spirogyra-tannin. 
1) CG. vaN WisseLINGH, Ueber den Nucleolus von Spirogyra. Bot. Zeit. 1898, p. 
202 — Ueber abnermale Kernteilung, |. c. 1903, p. 217, 
