566 SUMMARY OF CURRENT RESEARCHES RELATING TO 



typical ovoid and round yeast-cells, and in the older cultures a few 

 sausage-shaped, and many irregular cells also, some of the latter con- 

 taining spores. 



Reproduction by budding in a typical yeast-like manner is the usual 

 method of growth, the optimum temperature being 25°-30° C. Repro- 

 duction by spores occurs under the usual conditions of spore-formation 

 for tbe Saccharomycetes. The spore-containing cells differ from those 

 of most other Saccharomycetes in being compound cells, which have 

 conjugated by means of a beak developed from each, the tips of the 

 beaks fusing after the manner of many Algae and Fungi. In a few 

 hours after fusion, as observed in hanging drops of distilled water, the 

 protoplasm began to contract in the cells, and small round masses were 

 formed ; these eventually developed into the spores. The size of the 

 ripe spore is 4—5 jx, and the number in each compartment of the mature 

 cell varies from 1 to 4, the most common arrangement being 2 in each. 

 The spores germinate in a normal manner ; after swelling they bud like 

 ordinary yeast-cells. The irregular-shaped cells are apparently such as 

 have made attempts at spore-formation, but have failed, owing either to 

 lack of energy or substance in themselves, or to unfavourable external 

 conditions. Stained preparations showed that the tips of the beaks are 

 occupied by a deeply stained mass which is nuclear in character. The 

 two masses fuse together, and afterwards divide into two again. Hence 

 the process may be regarded as a simple sexual act somewhat similar 

 to that occurring in the process of spore-formation of Schizosaccharo- 

 myces octosporus. 



Alcoholic fermentation is produced in beer- wort by this yeast. It 

 also ferments levulose vigorously and dextrose and saccharose slightly. 

 Maltose, lactose, and dextrin are not fermented. 



The author regards the fusion process as a true sexual process, such 

 as is now known to occur in many fungi ; aud, as all the other characters 

 of this yeast accord with those of Saccharomyces, proposes to place it in 

 a new genus Zygosaccharomyces. 



Sporulation of Schizosaccharomycetes.* — A. Guilliermond, from a 

 study of Schizosaccharomyces octosporus, confirms the observations of 

 Schiouning relative to the formation of asci from the fusion of two 

 cells. He has also observed the presence of a nucleus consisting of a 

 nucleole surrounded by a zone of nucleoplasm and a limiting membrane. 

 The nucleus divides and afterwards participates in the fusion. Hence 

 in S. octosporus conjugation precedes the formation of asci, and the 

 phenomena may be regarded as a clear case of isogamy. 



In Schizosaccharomyces Pombe analogous phenomena may be observed, 

 and the histological appearances which accompany the conjugation of 

 the two gametes are practically identical with those in S. octosporus, i.e. 

 the protoplasm of the ascogenous cell is completely hollowed out into 

 vacuoles containing a number of red grains which persist after the 

 formation of spores in the epiplasm. The nuclei of the two primitive 

 cells blend in the junction-tube, then the nucleus resulting from the 

 fusion divides after a while into two daughter nuclei, which migrate 

 back to the cells, where they participate in the formation of two spores 

 at each of the two extremities of the ascus. 



* Comptes Rendus, cxxxiii. (1901) pp. 242-4. 



