5 
water. Finally the material was placed in Flemming's 
mixture, in which it remained some days, until the treat- 
ment with chromic acid yielded the desired result, namely, 
slow solution of the cytoplasm and chromatophores and 
isolation of the nucleus. The latter afterwards gradually 
dissolves, during which process some of the more resistant 
parts become very clearly visible. No contraction or 
coalescence of the protoplast should occur. Should this 
happen as the result of a faulty application of the method, 
the material is useless. The strength of the chromic 
acid solution, which I applied, was 10 or 25°/; Some- 
times the chromic acid, when it had acted sufficiently, 
was washed out with distilled water and the prepara- 
tions were stained blue by means of “Brilliantblau extra 
grünlich”. 
The preliminary treatment with alcohol and ether was 
advantageous and unaccompanied by any drawback. The 
troublesome fat was got rid of and it seemed to me that 
the fixation of the nuclei in Zygnema was even better 
than by the direct action of Flemming's mixture. I did 
not see the cavity round the nucleolus, which Escoyez 
named cavité périnucléolaire, and regarding the existence 
of which in the living object there are also differences of 
opinion in other cases. Therefore Î assume that no such 
cavity occurs in the living material and this agrees with 
the results [| obtained previously with other plants. 
Resting nucleus (Tab. I, Fig. 1). The nucleusis situated 
in the middle of the cell between the two chromatophores 
and is stretched longitudinally. The following parts can be 
distinguished in the resting nucleus: the nuclear membrane, 
the network composed of small granular bodies united by 
fine threads, and the nucleolus. I never saw a resting 
nucleus with two nucleoli. There is nothing special to 
say about the nuclear membrane and the nuclear network. 
With regard to the latter there is here as little reason 
