By this method several races of Saccharomycetes and brewery yeasts were isolated and described.
Previously to Hansen's work the only way of differentiating I Hansen found there were three species of spore-bearing Saccharomycetes and that these could be subdivided into varieties.
Hansen showed that the microscopic appearance of film cells of the same species of Saccharomycetes varies according to the temperature of growth; the limiting temperatures of film formation, as well as the time of its appearance for the different species, also vary.
With regard to the first question no satisfactory proof has as yet been given that Saccharomycetes are derivable by culture from any higher form, the recent statements to that effect not having been confirmed.
Such, in brief, are the methods devised by that brilliant investigator Hansen; and these methods have not only been the basis on which our modern knowledge of the Saccharomycetes is founded, but are the only means of attack which the present-day observer has at his disposal.