MORPHOLOGY AND ANATOMY OF YEAST CELLS. 301 



developed by Hansen and Strassburger, and later by Dangeard, 

 Janssens, Wager, Buscalioni, Hoffmeister, Rayman, Kruis, and 

 Guilliermond. We owe much to the fundamental studies 

 and the beautiful and careful drawings of Guilliermond. 

 The nucleus has a rounded form, and appears to enclose a 

 still smaller nucleus. When the yeast cell begins to bud or to 

 form spores, the cell nucleus propagates by division (Fig. 51), 

 and this division takes place before the budding or formation 

 of spores becomes visible. In connection with the fusion of 

 spores observed by Hansen in S. Ludwigii, Guilliermond proved 

 that a fusion of the nuclei takes place. He also observed 

 this phenomenon in the case of S. octosporus. 



The vacuoles constitute another essential part of the cells. 

 They separate gradually from the protoplasm of the young 

 cells, and appear in increasing numbers as pale, feebly-re- 

 fractive specks. In the older cells they are sharply defined, 

 and may assume highly irregular forms. In the Mycodermctr 



Fig. 51. S. Ludwigii. Nucleus division during pore-formation (after Guilliermond). 



species one or two very large vacuoles are usually found, and 

 this applies also to the old Saccharomyces cells. The vacuolea 

 are filled with an aqueous liquid, and often enclose fine granules. 

 The yeast cells also contain larger and smaller particles of 

 different refractivity, both in the protoplasm and in th& 

 vacuoles, which are classed together under the name of granules. 

 They are produced even in quite young cells. At a later stage, 

 when the cells are filled with glycogen, they are not so obvious, 

 but they are sharply defined when the glycogen has disappeared, 

 and they may assume large proportions in the dying cells. 

 Amongst those who have specially investigated the granules 

 Eisenschitz, Raum, Zimmermann, Will, and Guilliermond may 

 be mentioned. In many of these bodies, which doubtless vary 

 in composition, oily or fatty substance have been detected,. 



