1899] ABOUT YEAST 1S1 



euzyme which can be extracted by appropriate means, and will set up 

 fermentation in sugar-solutions under conditions which preclude any 

 activity of living plant-cells. The process was a perfectly normal one, 

 accompanied by the diminution of the sugar, the production of carbonic 

 acid gas, and the formation of alcohol. The enzyme is easily decom- 

 posed, and therefore rapid manipulation during the jDrocess of extrac- 

 tion is necessary. The secretion is shown to be intermittent, occurring 

 only during actual fermentation, and as the enzyme is soon decomposed 

 when the activity ceases, it is not found in the resting state of the 

 plant. Owing to these peculiarities Prof. Green failed to extract any 

 of the ferment in his former experiments. Dr. Buchner obtained the 

 enzyme by subjecting the yeast to high pressures applied by an 

 hydraulic press, but Prof. Green finds one of five atmospheres quite 

 sufficient. 



In the same number of the Annals Mr. Wager supplies an inter- 

 esting addition to our knowledge of the cytology of the yeast-plant. 

 The presence or absence of a nucleus has been matter of considerable 

 dispute. While such a structure has been described by many ob- 

 servers, others have declared the so-called nucleus to be merely a mass 

 of proteid or a vacuole. Mr. Wager has made several contributions to 

 the literature of the subject, speaking for the nucleus, but the one just 

 published seems to put the matter beyond doubt. He describes — and 

 his paper is accompanied by a large series of excellent figures — a 

 structure which he states is invariably present in the cells, and which 

 is a perfectly homogeneous body resembling a nucleolus rather than 

 the nucleus of the ordinary plant- cell. In the earlier stages of 

 fermentation this nucleolus is in close contact with a vacuole which 

 contains a granular chromatin-network, and shows a structure in many 

 cases like the chromatin-network of the nuclei of higher plants. In 

 the later stages of fermentation the chromatin- vacuole may disappear, 

 its place being taken by a granular network or a number of chromatin - 

 granules which may be disseminated through the protoplasm or grouped 

 around the nucleolus. Numerous vacuoles are often found in young 

 cells; these apparently fuse to form the single vacuole already de- 

 scribed. In the process of budding, the division of the nuclear 

 apparatus does not show any definite stages of karyokinesis, but is to 

 be regarded as a direct division of the nucleolus into two equal or 

 nearly equal parts, accompanied by division of the chromatin-vacuole 

 or network. In spore formation the chromatin disseminated through 

 the protoplasm becomes more or less completely absorbed into the 

 nucleolus which then divides. 



One feature of Mr. Wager's work is the cutting of microtome 

 sections of yeast-cells after imbedding and hardening in paraffin. The 

 absence of karyokinetic stages in the division of the nuclear apparatus 

 will perhaps still leave room for doubt in the minds of some cyto- 

 looists as to the true nuclear character of the structures described. 



