CYTOLOGY OF SACCHAROMYCES CERVICI/E. 44! 



from that of Phaseolus. A fruitful study of the finer points of 

 the structure of the resting nucleus as well as following it through 

 division would have been impossible without some means of 

 staining it without affecting the metachromatin. It is this 

 feature of our technique which makes the observations con- 

 vincing. A centrosome could not be identified in the interkinetic 

 cell nor could any variation in the cytoplasm surrounding the 

 nucleus, comparable to sphere substance, be seen. 



The yeast cell contains both fat and glycogen, the former 

 usually in small globules in the vicinity of the nucleus. 



It has been previously observed that yeast cells will give off 

 a gelatinous secretion when permitted to dry gradually in a closed 

 vessel. This is thought to play a part in the agglutination of 

 yeast and the consequent clearing of the medium. In the 

 present work it was found that dilution of the medium of an 

 old culture with distilled water will produce this secretion 

 (Fig. 9). The secretion has great affinity for light green. 



BUDDING. 



In young cultures the usual method of reproduction is by 

 budding. The superficial features of this process are matters of 

 common knowledge, and consequently, this description will be 

 limited to the internal phenomena. The bulge in the cell wall 

 and the entrance of cytoplasmic elements into the bud occurs 

 some time before any change in the resting nucleus is observable 

 (Fig. 14). The finely vacuolated cytoplasm is the first material 

 to enter the bud. This is followed by the metachromatic 

 granules. In those cells that contain a large vacuole the bud 

 is generally formed near the nucleus and consequently near the 

 greater part of the metachromatic material. The mass of this 

 material near the bud separates into individually visible granules, 

 part of which migrate through the isthmus into the bud, the 

 rest moving to the opposite side of the parent cell (Figs. 15 and 

 21). Whether or not they divide at this time cannot be stated. 

 Even after these granules are distributed to the two cells the 

 nucleus is still in the resting condition. The large clear vacuole 

 does not divide, but after the bud has attained almost the size 

 of the parent cell a small vacuole appears within it and gradually 

 enlarges. 



