verj thin membrane. He tliinks it possible, however, that this cavit^^ 

 is formed in the fixing. He describes the nucleolus as mostly sphe- 

 rical and homogeneous; in some cases it shows an irregular, very 

 aberrant form. 



EscoYEZ states tiiat during the prophase of karyokincsis thicker 

 parts arise in the network which shows a looser structui-e. Fiiuiily 

 30 to 40 chromosomes are formed which resemble rod lets. 



The chromosomes arise directly from the network wliicii does not 

 first form a spirem. The nucleolus plays no morphological part in 

 the formation of chromosomes. Its shape undergoes modification 

 and finally it completely dissolves. Escoyez states that tiie nuclear 

 spindle penetrates into the nuclear-cavity and that the chromosomes 

 subsequently form an equatorial ring. Then longitudinal splitting 

 takes place, the chromosome halves take u|) a position near the two 

 poles of the nuclear spindle, which are found near the chromato- 

 pliores. They crowd together into plate-shaped bodies. Later they 

 again become visible to the number of 30 to 40. Gradually a net- 

 work forms which corresponds with that of the resting nucleus. 

 EscoYEZ says that the nucleolus is first a small body which gradu- 

 ally increases in size. Its formarion is independent of the chromosomes. 



The object of Escoyrz's investigation was not only to control Miss 

 Merriman's results, which diverge greatly from those generally obtained 

 in karyokinetic inqqiry, but he wished also to answer the question 

 whether Zygnema so far as the nucleolus and karyokinesis are concerned, 

 agrees with Spirogym where according to Escoyez J Bekghs ^) has 

 established that the twelve chromosomes arise exclusively derived 

 from the nucleolus. As is already evident from the above, Escoyez's 

 investigation yielded negative results on both points. His results 

 differ widely from tiiose of Miss Merriman and also from those of 

 Berghs obtained with S/nroyyra. 



With regard to the latter, I remark, that the opinions of investi- 

 gators on the nucleolus and karyokinesis of Splroyym are very 

 divergent and that weighty objections can be advanced against the 

 conclusions of Berghs in particular '^). 



The object of my own incpiiiy was to answer the quesüon 

 concerning the agreement of the two genera in respect of the nucleoli 

 and karyokinesis, of which I had ab-eady made a complete study in 

 five species of Spiroyyra. The results obtained with three thick 



1) J. -Berghs, Le Noyau el la Cinèse cliez le Spirogyra, Exlxail de la Revue ""La 

 Cellule", t. XXllI, ler fasc. li;06, p. 55—85. 



■-) G. VAN WissEUNGH, Ueber die Karyokinese bei Oedogonium, Beiliefte zum 

 Botan Ccntralblatt. Bd. XXIII (1907), Abl. I. pag. 152 and foil. 



