ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 205 



Cytology of Yeast.* — A. Guillermond has published an important 

 work on this subject. He gives a historical account of previous research, 

 and details the methods employed, then follows the account of work done 

 on special forms of the genera Saccharomyces, Schizosaccharomyces, and 

 Dematium. In all yeast-cells he finds a nucleus that divides by direct 

 division. In discussing the genus Schizosaccharomyces, he describes the 

 process of copulation of the yeast-cells and their nuclei which precedes 

 spore-formation. After fusion, the nucleus divides and the daughter- 

 nucleus goes back to the cell from which the fusing nucleus had passed 

 over ; both nuclei divide equally to form spores. In other yeast-forms 

 copulation has not been found. 



Study of Nuclei in Yeast and Animal Cells, f — Feinberg has 

 devoted his attention to the form of the nucleus in one-celled organisms 

 with special reference to yeast, the amcebas of Myxomycetes, fresh-water 

 rhizopods, and sporozoa. With the exception of yeast he finds that there 

 is no nucleolus in any of the nuclei examined, and no nuclear fibrils 

 corresponding to that of plants and animals. As an equivalent they 

 possess a chromatin body which he terms a nuclear point (Kernjnmki} 

 and which is surrounded by nuclear sap. 



Yeast. X —Albert Hirschbruch discusses the condition of the yeast- 

 cells in old cultures. He finds in many of them that the nucleus has 

 broken down and he describes three stages in this process of degeneration 

 ending in the total disappearance of the nucleus. He has not determined 

 yet at what stage of degeneration the cell loses the power of multipli- 

 cation, nor to what extent these degenerated cells can be revivified. 



Fritz Thibaut § contributes a paper on the influence of the alcoholic 

 fermentation products on the yeast-plant and on the process of fermen- 

 tation. 



Life-history of Yeasts. || — Emil Chr. Hansen studied this subject 

 first with Saccharomyces apiculatus. He found that this yeast was 

 present on fruits all through the ripening season, transported from one 

 to the other by the agency of insects and especially wasps. It was 

 washed off by rain or was conveyed to the ground with falling fruit and 

 wintered in the soil. The wind was a sufficient agent in again trans- 

 porting it to ripening fruit the following summer. The connection 

 between the soil and the fruit was so close that this particular yeast was 

 never found in soil far removed from fruit-bearing plants. Hansen 

 found for other species of Saccharomyces that their life-history was very 

 similar ; only, though they were most abundant in gardens, they were 

 also to be found in soils everywhere. The reason of this, Hansen found, 

 was that those other yeasts increase more abundantly in the moisture of 

 the soil and sustain life longer in water. They can thus be more readily 

 transported in a living condition in water than can S. apiculatus. 



* 'Recherches cytologiques sur les levures et quelques moisissures a formes 

 levures,' Lyon, 1902, 289 pp. and 12 pis. See also Hedwi°;ia, Beibl., xli. (1902) 

 p. 233. f Ber. Deutsch. Bot. Ges., xx. (1902) pp. 567-77 (1 pi.). 



J Centralbl. Bakt., ix. (1902) pp. 737-43 (1 pi.). 



§ Tom. cit., pp. 743-6. || Op. cit., x. (1903) pp. 1-S. 



