270 YEASTS AND YEAST-LIKE FUNGI 



are referred to in German literature as "Dauerzellen" and are, func- 

 tionally at least, identical with the chlamydospores of mycelial 

 fungi. 



Since yeasts behave like higher organisms with regard to genetics, 

 the importance of the nucleus has had renewed interest in recent 

 years. What is known, however, is not in proportion to the impor- 

 tance of the subject. Bacteriologists, particularly, are interested be- 

 cause yeasts seem but a step higher than bacteria in complexity as 

 well as size. Most of the work on nuclei in yeasts, like nearly all of 

 it with bacteria, will have to be discounted since volutin (often 

 called yeast nucleic acid) has not been distinguished from the chro- 

 matin which is characteristic of the nucleus. Most of the drawings 

 and photographs in textbooks labeled nuclei may as well be and 

 probably are metachromatic granular material. While the early 

 cytologists may in some cases have demonstrated the nucleus (Moel- 

 ler in 1893 probably, and Guilliermond in 1901 almost certainly, 

 demonstrated them), the Feulgen reaction in the hands of Rochlin 

 and Badian has established its presence beyond reasonable doubt. 

 Although the presence of nuclei in yeasts is established, the size (less 

 than 1 micron in diameter) is such that we still lack accurate knowl- 

 edge on details as to chromosomes and behavior during budding, 

 fission, conjugation, and spore formation. The remaining structures 

 in the protoplast are reserve foodstuffs and may be discussed under 

 three heads: fat, carbohydrates, and proteins. 



NFat appears at times in old cultures as highly refractile vacuoles. 

 At first these are usually numerous and small, but as the cell grows 

 older they tend to coalesce and form one large vacuole which may 

 nearly fill the cell. Such large fat vacuoles are very characteristic 

 of certain species of yeasts. Their fatty nature may be readily 

 demonstrated by staining with Sudan III. \Carbohydrate, as in the 

 more complex fungi, is stored as glycogen and can be demonstrated 

 by suspending some of the culture in dilute Lugol solution and ex- 

 amining microscopically under a cover glass. The glycogen granules 

 stain a deep reddish brown, the rest of the cell a pale yellowish 

 brown. Protein occurs in the cytoplasm in the form of fine granules 

 which have been studied by Kohl and by him designated albuminous 

 granules. They may be demonstrated by overstaining with the basic 

 dyes and then differentiated by some decolorizing agent. For this 

 purpose Gram's stain serves admirably. 



In connection with these albuminous granules some observations 

 by R. and W. Albert and by Henrici are of interest, since they per- 

 haps throw some light on the nature of Gram's stain as well as of the 



