MYCODERMA CELLS. 409 



Even as recently as 1871 we find Trecul expressing the view 

 that proteid materials can change themselves into bacteria or 

 direct into beer yeast, these again into Mycoderma, and the latter 

 in turn into Penicillium (see p. 107, vol. ii.) ; and similar ideas 

 are found in a treatise by HOFFMANN (VII.) in 1869. At the 

 same period, however, ADOLF MAYER (X.) disputed the alleged 

 genetic relation between yeast and My coder ma ^ and between 

 yeast and Penicillium; and REESS (IV.), in 1870, denied the 

 identity of Penicillium , wine yeast and Mycoderma. 



Moreover, the old assumption that the so-called /Sacch. Myco- 

 derma (see p. 271, vol. ii.), Mycoderma vini and Myc. cerevisice 

 were one and the same species, has been disproved by the 

 numerous researches of later workers. The paths by which this 

 knowledge was attained are identical with those pursued by 

 Hansen in establishing the existence of the different races of 

 beer yeast, namely, by the pure culture of the organisms, and 

 by accurate morphological and physiological investigation. 



There is no difficulty in obtaining material for the pure culture 

 of different races of Mycoderma. Bottled wine, fruit wine, beer, 

 &c., low in alcohol, is taken, half the contents of each bottle 

 being poured out, and the remainder shaken up once or twice, 

 after which the bottles are plugged with cot ton- wool and are left 

 to stand for several days at about 20 0. This treatment admits 

 a sufficiency of oxygen to the bottles and liquids, so that the Myco- 

 derma species and other organisms present therein are enabled to 

 develop. Pure cultures of these organism scan then be prepared 

 by the method recommended by Hansen (see p. 278^ seq., vol. ii.). 



The various races of Mycoderma can be differentiated by the 

 size and shape of their cells, their rate of reproduction growth 

 in giant, stab and streak cultures, the character of the super- 

 ficial vegetation, and by the attendant phenomena of the same. 

 Physiological examination also reveals differences between the 

 various species that may also indicate racial peculiarities. 



303. Form, Dimensions and Contents of 

 Mycoderma Cells. 



Attempts to identify single or mixed races of Mycoderma by 

 microscopical examination alone meet with exactly the same diffi- 

 culties as are encountered in the corresponding investigation of 

 beer and wine yeasts, the problem being still further complicated 

 by the fact that the development of Mycoderma in must or other 

 nutrient media is accompanied by numerous morphological 

 changes, whereas the true wine yeasts, for example, retain their 

 form practically throughout such treatment. Mycoderma species, 

 on the other hand, and especially while young, sometimes vary 

 in form to such an extent that the observer might be led to 

 think the cultures had become contaminated, if he had not, by 



