CVTOLOGy 



6-10 



centrosome. Occasionally the bud-opening is too small to permit 

 the contents of the vacuole to enter the bud and the canal is disten- 

 ded at this point like the esophagus of an ostrich swallowing an or- 

 ange. A bulb is produced at the end of this process to form the bud- 

 vacuole. During this period the centrosome is a hemispherical solid 

 unyielding structure that is not deformed by movements of bodies 

 near it. After the bud-vacuole is formed the centrosome divides. 

 After the division of the centrosome is completed and the establish- 

 ment of contact of bud-vacuole and bud-centrosome has been attained, 

 the interconnecting canal between the mother- and bud-vacuole dis- 

 appears. 



Fig. 6-5. Outline Drawings Showing the Vacuole and its Processes in Yeast 

 Cells. The centrosome is stippled. 



As soon as the bud approaches the size of the parent cell, the 

 nuclear apparatus in bud and mother cell reorient themselves so 

 that the centrosome in each cell is distal to the bud partition. 



THE MITOCHONDRIA 



In the cytoplasm of a resting (nonbudding) yeast cell one finds 

 a variable number of mitochondria; some cells contain fifty or more 

 (fig. 6-6). When the cell begins to divide they dissolve and the cyto- 

 plasm becomes optically homogeneous. These bodies in Saccharo- 

 myces were called basophilic granules by Guilliermond (1910) be- 

 cause they stained with basic dyes. In an ultramicroscope study of 

 Saccharomycoeds (1932) he called the identical granules "lipoidal 

 granules" because of their high refractivity. Fig. 6-7 shows a phase 

 difference photograph of Saccharomycodes demonstrating the mito- 

 chondria. Wager and Peniston (1910) and Caspersson and Brandt (1941) 

 called them volutin granules. I (1947) have pointed out that this is er- 

 roneous, since volutin does not occur in cytoplasm of living cells. 



Caspersson and Brandt showed by precise ultraviolet micro- 

 scopy that the cytoplasmic granules contain ribosenucleoprotein. 



