HEMIASCOMYCETES 



273 



that in Schizosaccharomycetes a simple form of sexual re- 

 production is also present. Two adjoining cells put out 

 protuberances that meet and fuse, the cell-wall disappear- 

 ing at the point of junction. Eventually the neck expands 

 and with the two conjugating cells forms a large oval cell, 

 or in some instances the neck does not expand, and a more 

 or less hour-glass form results. A nucleus from each con- 

 jugating cell passes in to the neck, and these two fuse when 

 fusion of the cells has taken place. The fusion-nucleus 

 afterwards divides to form two daughter-nuclei, which by 

 repeated division form the nuclei of the spores. 



In Schizosaccharomycetes octosforus eight spores are 

 constantly present in the ascus. 



The cell containing endogenously formed spores is con- 

 sidered as an ascus, hence the Saccharomycetes are included, 

 in the wider sense, in the Ascomycetes, but on account of 

 the entire absence of a perithecium or protective covering 

 are grouped with the Hemiascomycetes, their nearest 

 affinity being with some of the simpler genera as Endo- 

 myces, included in the Gymnoasceae. 



The question as to the presence of nuclei in yeast has 

 been much discussed of late. Wager has investigated this 

 matter in an exhaustive manner. The following is his 

 summary : 



' i. All cells of yeast contain a nuclear apparatus. 



' 2. In the earlier stages of fermentation this consists of 

 a nucleolus in close contact with a vacuole which contains 

 a granular chromatin-network, and exhibits a structure in 

 many cases like the chromatin-network of the nuclei of the 

 higher plants. 



* 3. In the latter stages of fermentation the chromatin- 

 containing vacuole may disappear, its place being taken by 



