HISTORICAL, DELIMITATION, DERIVATION. 385 



greasiness which causes the cells tc adhere superficially. This 

 feature, however, is not a strong one. 



The species shown in Fig. 5 of the Plate in question is 

 morphologically similar to an ordinary yeast (Saccharomyces), but 

 probably also belongs to the Torulacece. 



Pasteur himself expressed doubt as to whether all the forms 

 depicted represented an equal number of species, and showed (as 

 illustrated in his Figs, i and 2) that the elongated cells could also 

 produce those of the small, globular type. He held the opinion 

 that different varieties could be obtained from a Torula species 

 with mixed cells, by sowing the different cell forms. Although 

 he adduced no proofs in support of this, it is nevertheless correct, 

 the more so because as we now know there are Torula forms 

 which, under the influence of a certain environment, reproduce 

 almost exclusively in the form of small, more or less globular, 

 cells, the elongated cells being comparatively small in number, 

 whilst under other conditions these latter calls becomemore 

 prominent. 



Pasteur mentions, as a chief characteristic of the Torula forms 

 depicted in his Figs. 1-6, that, like Mycoderma, they are unable 

 to set up alcoholic fermentation. 



Although Pasteur was able to characterise a series of the chief 

 representatives of the Torulacece with a fair amount of certainty, 

 notwithstanding that he was not in possession of absolutely pure 

 cultures, the line of demarcation between them and the Saccha- 

 romycetes is uncertain and imperfect ; and among them may be 

 found Saccharomycetes with weak powers of fermentation. 



It was not until the researches of HANSEN (XXIV.) that the 

 two could be more effectually separated. This worker applied the 

 name Torula to budding fungi which produce neither endospores 

 nor typical mould vegetations, thus differentiating them from the 

 Saccharomycetes on the one hand and from Monilia, Dematium 

 and other budding Hyphomycetes on the other. 



By this definition Hansen greatly restricted the morphological 

 circle of the Torulacece, allocating to the latter only such species 

 as produce cells of a more or less globular shape, although some 

 of his species form elongated, sausage -shaped cells in film vegeta- 

 tions. In any event, this limitation excludes from the Torulacece 

 all the asporogenic budding fungi resembling Mycoderma, as also 

 Mycoderma itself. Moreover, whilst Pasteur's Torulacece set up 

 merely a very weak fermentation, or none at all, the species 

 classified by Hansen exhibit all gradations in this respect, a few 

 of them setting up a fairly vigorous fermentation. Consequently, 

 Hansen's Torula species (see pp. 9, 10, vol. ii.) cannot be un- 

 conditionally united in one group with those of Pasteur. 



The faculty of sporulation excludes from the Torulacece all 

 such of the Saccharomycetes as like the species Torulaspora 

 Delbrilckii(see p. 284,vol. ii.) of P. Linder (XXXVI.), and another 



