SACCHAROMYCETES. 249 



certain precautions against accidental contamination from air-borne 

 spores. The neglect of such precautions in former experiments of 

 like nature had led to the invasion of various moulds, and had 

 given rise to the now exploded pleomorphic theory. The cells 

 thus placed under suitable conditions for observation, were main- 

 tained at a medium atmospheric temperature for some days. At 

 first, some development by the ordinary process of sprouting took 

 place, so that the circumference of the patch of yeast extended itself 

 beyond the space originally occupied; but the new cells produced 

 had few or no vacuoles, and, at the end of three or four days, this 

 method of increase entirely ceased, and the character of all under- 

 went a change. Some cells appeared empty and died out, in others 

 the protoplasmic cell contents assumed a granular appearance, and 

 in a few hours showed a tendency to concentration on independent 

 points within the cell. This increased until several distinct proto- 

 plasmic masses were formed, which eventually became covered 

 with their spherical envelopes while still remaining within the 

 mother cell, the wall of which had distended and, at the same time, 

 gained in tenuity. 



When this development appeared to be fully matured, these 

 compound cells were placed in suitable nutritive liquids, and in a 

 short time new cells were produced, not from the mother cell, but 

 by the budding of the newly formed spores, these buds penetrating 

 through the old cell wall, which speedily disappeared. The cycle 

 of changes was thus found to be complete, and the constancy of 

 the organism under the altered conditions of reproduction (which 

 had hitherto been fiercely disputed) was fully established by the 

 demonstration of a stage in its history which proved its proper 

 position to be among the ascomycetes, and which fungologists at 

 once recognise as a form of spore formation in an asciis^ the 

 mother cell itself constituting the ascus. 



The next step of importance undertaken was to ascertain how 

 far this process of ascospore formation is general among the organ- 

 isms known to cause alcoholic fermentation, and here the work was 

 taken up by the able hands of Dr. Chr. Hansen, of the Carlsberg 

 Laboratory, at Copenhagen. Seeking for a character which should 

 enable him to define the genus Saccharomyces, this skilful 

 observer made an exhaustive investigation^, and found that those 



