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nesis a body appears, which plays an important part, namely 
the central spindle (Zentralspindel), a body which does not occur in 
higher plants, but is specially found in Diatomaceae. During karyo- 
kinesis the nucleolus and the nuclear membrane disappear. The net- 
work forms a skein {Knäuel) and by segmentation the chromosomes 
arise out of it. They are long and well-formed. In Nitzschia 16 appear 
and more in Surirella. In the middle the chromosomes form a ring 
round the central spindle. By division of this ring there arise two 
rings which separate from each other along the central spindle. Hach 
of these rings consists of the halves of the chromosomes. The 
daughter nuclei develop from the rings. 
Shortly after LAUTERBORN a paper was published by K1LEBAHN') on 
karyokinesis in Rhopalodia gibba. (Ehrenb.) O. Müller. He describes 
the diaster stage and mentions the central spindle and the chromo- 
somes which to the number of 5 or 6 are placed in a circle and 
are granular in shape. 
Some years later Karsten’) described in detail the karyokinesis of 
Surirella saxonica. In general his results agree with those of LAurrr- 
BORN ; in one point however they disagree greatly, for Karsrrn found 
the chromosomes in Surirella calcarata and other Diatomaceae short 
and of irregular shape in complete contrast with the observations 
of LAUTERBORN. 
In October 1903 I found an Eunotia in a ditch near Steenwijk. 
After further examination and consultation of the descriptions and 
drawings of the various species *), I assumed that the specimen found 
was Eunotia major Rabenh. In the healthy, although not plentiful, 
material I saw numerous stages of karyokinesis, and since this pheno- 
menon had not yet been described in Eunotia, I determined to utilise 
this opportunity of studying it. 
The living object was first investigated, and then material which 
had been fixed with HrpMMiNG’s mixture. In order to study the 
karyokinetic figures better I treated the fixed material with a solution 
of chromic acid of 20°/,. Various constituents of the cell-contents 
successively dissolve in it and finally there remains inside the 
siliceous skeleton of the cell-wall, when the cells contain no fatty 
oil, only the nuclear network, or what results from it. The prepa- 
1) H. Kuesaun, Beiträge zur Kenntnis der Auxosporenbildung, I. Rhopalodia gibba 
(Ehrenb.) O. Müller, Pringsheim’s Jahrb. f. wiss. Bot. Bd. 29, 1896, p. 595. 
2) G. Karsten, Die Auxosporenbildung der Gattungen Cocconeis, Surirella und 
Cymatopleura, Flora, 1900, Bd. 87. p. 253. 
3) L. Dippet, Diatomeen der Rhein-Mainebene, 1905, p. 125. 
Van Heurck, Traité des Diatomées, p. 298. 
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