CHAPTER II 

 CYTOLOGY OF YEASTS 



General Considerations. Historical 



FOR many years the cytology of yeasts has been concerned with 

 the nucleus. Do yeasts have nuclei like other organisms? Or, 

 on the contrary, are they deprived of a nucleus and therefore an 

 exception? The question of a nucleus in the yeasts has given rise to 

 a great number of reported investigations which allow contradictory 

 conclusions. Some authors, among others Dangeard, Janssens, 

 LeBlanc, Bouin, etc., have described bodies in yeasts which seemed 

 to them to be nuclei; but others, having noticed a great number of 

 disseminated particles in the cells, have admitted the presence of a 

 " Diffused Nucleus." They believe that the chromatin is more or 

 less mixed with the protoplasm of the cell and sometimes condensed 

 in the form of colored grains. Eischenschitz, having noticed that 

 these grains were particularly abundant in the vacuole, admitted 

 that this last was a sort of rudimentary nucleus. 



This conception was specified by Wagner 1 in 1898 and again 

 by Wagner and Peniston. 2 These authors described in the yeasts, 

 first, a vacuole, vacuole nucleare, filled with chromatin particles, and 

 secondly, a nucleole of homogeneous appearance, situated at the 

 exterior of this vacuole but always close to it. The whole of this 

 vacuole is filled with particles of chromatin and, according to these 

 authors, is a rudimentary nucleus representing a primitive step in the 

 phylogenetic development of the nucleus. 



Guilliermond 3 has given this debated question of yeast structure 

 much study since 1901. It has been shown that the interpretation 

 of Wagner is inexact, and the yeasts have a structure identical with 



1 Wagner, H. The nucleus of the yeast plant. Ann. of Botany, 12, 1898. 



2 Wagner, H., and Peniston, A. Cytological observations on the yeast plant. 

 Ann. of Botany, 24, 1910. 



3 Guilliermond, A. Recherches sur la structure de quelques champignons 

 inferieurs. Comp. Rend. Acad. des Sciences, 133, 1901. Recherches histologiques 

 sur la sporulation des levures. Comp. Rend. Acad. Sci. 133, 1901. Recherches 

 cytologiques sur la levure. Thesis for Doctor of Science, Paris, 1902. Re- 

 marques sur differentes publications parues recemment sur la cytologie des levures, 

 Cent. Bot. 26, 1910. Nouvelles recherches sur la cytologie des levures. Comp. 

 Rend. Acad. Sci. 150, 1910. 



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