A Conjugating " Yeast." 



347 



are apparently produced from the ordinary ovoid or round cells during 

 efforts at spore-formation. Beaks are formed at different points of the 

 cell, but no conjugation takes place ; or, if it does occur, no spore 

 formation follows. Consequently cells of great irregularity in shape 

 result, and such may be considered as cells which have made attempts 

 at spore-formation, but have failed owing either to lack of energy or 

 substance in themselves, or to unfavourable external conditions. 



The behaviour of the nuclear contents during conjugation and spore- 

 formation is suggestive. Stained preparations of cells in different 

 stages of these processes show that the tips of the beaks are occupied 

 by a deeply stained mass, which on conjugation fuses with a similar 

 mass in the beak of the other cell which takes part in the process. The 

 fused mass then divides into two, one portion withdrawing into each 

 compartment of the compound cell ; there division again takes place, 

 in such a way as to provide the basis of each spore about to be formed. 

 Previous to the latter division a deeply stained and prominent granular 

 network becomes arranged around each mass, and this separates into 

 groups when the final division occurs, the number of groups corre- 

 sponding with the number of masses. 



By this time each mass is rounded off into a spherical body — the 

 young spore — and around each spore a group of granules is arranged 

 and eventually a wall is formed. The spores then ripen. Lack of 

 knowledge as to the exact nature of the yeast nucleus prevents a com- 

 plete interpretation of the histological facts observed, but it seems 

 certain that the deeply stained masses are nuclear in nature, and that 

 consequently a kind of nuclear fusion takes place. If so the process 

 must be looked upon as a simple sexual act, somewhat similar to that 

 occurring in the process of spore-formation of Schizo-saccharomyces octo- 

 sporus. 



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

 also ferments laevulose vigorously, and dextrose and saccharose slightly. 

 Maltose, lactose, and dextrin are not fermented. A mixture of dextrose 

 with maltose and dextrin is fermented more freely than dextrose alone. 

 Long-continued cultivation in beer-wort seems to have increased its 

 fermentative activity for that medium. 



In conclusion, there seem to be three possible views regarding the 

 nature of the fusion-process, viz. : (1) It is an abnormal or pathological 

 phenomenon due to the conditions of culture ; (2) it is a mere cell- 

 fusion, such as frequently occurs between contiguous cells in fungi; or 

 (3) it is a true sexual process, such as is now known to occur in 

 many fungi. 



The first view seems unlikely, since the result of the process is the 

 production of normal healthy spores, and the conditions are exactly 

 such as are generally efficacious in the production of spores in yeast of 

 all kinds. 



VOL. LXVIII. 2 B 



