YEASTS 65 



her of granules smaller than the nucleolus, and sometimes even found 

 gathered on the circumference of the nuclear membrane. 



The cytoplasm is dense and homogeneous. A special technic has 

 recently enabled the demonstration of a chondrium in the cytoplasm. 

 This seems to consist both of granular mitochondria and of more or 

 less elongated and flexible rod-mitochondria (Fig. 47). 



The vacuole shows in its interior numerous metachromatic corpus- 

 cles of varying sizes (Fig. 48). As in molds, these corpuscles appear not 

 only in the vacuole, but also in the perivacuolar cytoplasm; there they 

 start, and are next diffused in the vacuole where they finish their growth, 

 then dissolve when the need is felt. It is 

 difficult in the case of yeasts to determine , 

 their origin; nevertheless, observations ^ 

 made of fungi with larger cells than we 



~r j 



have previously described, show that the 



metachromatic corpuscles start in the .I;-!. 



midst of mitochondrial elements, and it r" 



seems certain that after that the process 5 6 I 



is the same in yeasts. FIG. 48. Saccharomyces cere- 



Tn the rvtonla^m of vpasts a ho have visi<B > stained b y a method re- 

 cytopiasm yea. ,s, ai o, nave vealing both ^ nuc i eus and 



been noted granulations, which can be the metachromatic corpuscles, 

 stained with ferric haematoxylin, and which 



have been named basophile grains; but these formations, which are not 

 well defined, seem to us to represent simply products from the altera- 

 tion of the chondrium under the influence of imperfect fixing agents. 



The membrane of yeasts is quite thick and very distinct. Its 

 chemical nature is still little known. According to some authors, it 

 consists of a cellulose; others think that it contains only pectose. Ac- 

 cording to Mangin, it is formed of callose. Finally, some authors have 

 thought they discerned chitin. 



The structure we have just described is found in all the species 

 (Fig. 49), only it is sometimes much less distinct because of the smallness 

 of the cells. In the elongated yeasts, and in the cells composing the 

 mycelial formation which are encountered under some conditions, 

 especially in the films, the nucleus generally occupies the center of the 

 cell; it is situated in a kind of matrix or bridge consisting of a very 

 dense cytoplasm, while a vacuole filled with metachromatic corpuscles 

 occupies each of the two extremities of the cell. 



5 



