THE YEASTS CHAPMAN 309 



the deeply staining structure in close contact with it, and which is 

 generally regarded as the nucleus, is to be looked upon as the nucleo- 

 lus. This is a view in which I have never felt myself able to concur, 

 although much, of course, depends on the precise meaning giA^en to 

 the words nucleus and nucleolus, respectiA^ely. 



In addition to the nucleus with a clearly differentiated structure 

 and a nucleolus, the cell contains cytoplasm, a chondrium, metachro- 

 matic granules, a nuclear and other vacuoles, and certain thread-like 

 structures. The cell wall, about which a good deal of uncertainty 

 exists, appears to consist as a rule of a single membrane, and to have 

 a complex chemical composition. 



In addition to these elements, which may be regarded to some 

 extent as structural, there exist in the cytoplasm accumulations of 

 materials concerned in the nutrition or metabolism of the cell, such, 

 for example, as glycogen and fat. 



With regard to the functions of these various cell elements it is not 

 yet possible to speak with very great certainty. As in all cells the 

 nucleus is the main seat, or rather the directing organ, of the physio- 

 logical functions of the cell. It is all important in cellular reproduc- 

 tion and division ; it plays apparently a prominent part in nutrition, 

 and doubtless in it reside the properties which are hereditary, and 

 in virtue of which one species Ta2ij be distinguished from another. 

 The chondrium, consisting of two forms of mitochondria, appears to 

 be concerned in processes of nutritional elaboration, and the nuclear 

 or main vacuole appears to be largely concerned with metabolic 

 processes, and is according to some observers the seat of fermentative 

 activity. This latter function has, moreover, been observed to be 

 dependent on the amount of metachromatic granules contained in the 

 cell, the larger the amount of metachromatin (volutin) the greater 

 the fermentative activity ; and Henneberg has gone so far as to sug- 

 gest that the metachromatic granules may be the parent substance 

 from which the enzyme zymase is derived. From this necessarily 

 brief and sketchy account of the yeast-cell anatomy it will at least be 

 gathered that our knowledge is very imperfect and that we have 

 much to learn, and it may be hoped that some of the expert cytolo- 

 gists who are members of our Society may be induced to turn their 

 attention to the elucidation of the subject. There can, I think, be 

 very little doubt that the results would be of important industrial as 

 well as of purely biological value. 



The ordinary microscopical examination of cells which have been 

 subjected to the drastic processes of fixing and staining obviously 

 has its limitations, and modifications of structure, such as must al- 

 most inevitably be brought about by the above processes, may very 

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