The Nucleus of Saccharomyces: A Cytological Study of a Frozen-Dried Polyploid Series

Identification of the yeast nucleus, and par-ticularly a resolution of its mitotic cycle, can scarcely be considered to have yielded unanimous agreement. In spite of a voluminous cytological literature, little has been established with cer-tainty in regard to the identity, morphology, or numbers of chromosomes, or in regard to the orientation of the dividing nucleus with respect to the centrosomes during budding. Incertitude and divergences of opinion on these questions have resulted partly from difficulties inherent in obtaining suitable preparations of organisms so small as yeast for cytological analysis, and partly from the fact that cytological studies were undertaken in almost all instances on cul-tures unknown genetically as to the number of linkage groups and the degree of ploidy.