428 



SCIENGE. 



[N. S. Vol. VIII. No. 196. 



ate conditions of Ustilaginacese. In fact, 

 one has only to consult Brefeld's own writ- 

 ings to see that Saccharomycetes-like bodies 

 are produced by the germinating spores of 

 other orders of fungi than Ustilaginaceas, 

 and it is known that, in some species, as in 

 the genus Aspergillus and in certain Mucora- 

 cese, the budding cells which look like the 

 Saccharomycetes, using the word in the 

 limited sense, are also capable of producing 

 alcoholic fermentation. 



On the other hand, no one has yet suc- 

 ceeded beyond a doubt in making the Sac- 

 charomycetes proper revert to a higher an- 

 cestral form. I say beyond a doubt, because 

 the observations of Juhler, Joergensen and 

 Johaa-Olsen on the relation of Asjiergillus, 

 Sterigmatocystis and Dematium to Saccharo- 

 mycetes have not been confirmed by other 

 equally good observers, as Kloecker and 

 Schioenning, and, for the present at least, 

 we must regard the observations of Joer- 

 gensen and Johan-Olsen as affording still 

 other instances of the fact that under proper 

 conditions the germinating spores of many 

 fungi produce bodies like Saccharomycetes, 

 while they do not show conclusively that 

 forms recognized by specialists as genuine 

 Saccharomycetes can be transformed into 

 fungi of other orders. They do, however, 

 show that the views of Brefeld that the 

 Saccharomycetes are derived from Ustilagi- 

 naceffi could, at the best, be only partially 

 true. 



Let us return to the question as to whether 

 or not species of the Saccharomycetes, as 

 defined by Hansen, for instance, should be 

 allowed to be called species in the proper 

 sense of the word. Of course, no one sup- 

 poses that they have always existed in their 

 present form and, although we have no ex- 

 act knowledge of the ancestors of the pres- 

 ent species, we naturally suppose that they 

 were derived from some other higher fungi, 

 as the expression goes. Whether derived 

 from one particular order or fungi or from 



several diflPerent orders, the species as we 

 now see them seem to be constant in the 

 sense in which that word must be used in 

 speaking of species of any group of plants. 

 The shape of the cells in any given species, 

 although variable to some extent, is constant 

 within definable limits and, although they 

 have periods of rest and periods of activity, 

 their physiological action seems to be the 

 same under similar conditions. 



We might be justified, it seems to me, in 

 regarding as races the Saccharomycetes- 

 like forms which result from the germina- 

 tion of spores of higher fungi, provided they 

 continued to live an independent existence 

 for a time and were not, as is more likely 

 to be the case, merely accidental conditions 

 depending on unusual or unfavorable con- 

 ditions of germination, but the Saccharo- 

 mycetes in the limited sense are constant, 

 as far as constancy is to be expected in living 

 organisms in general ; they cannot be made 

 to revert, as far as we know, and I there- 

 fore fail to see why they should not be ad- 

 mitted to be scientific species. The same is 

 true of the physiological species of bacteria, 

 meaning, of course, those which have been 

 well studied, and excluding the mass of ill- 

 described and ill-known forms which abound 

 in bacteriological writings. When a race 

 has become so constant that it no longer re- 

 verts, and we cannot tell from what species 

 it came, it is no longer a race, but a species. 



It may be objected, however, that both 

 bacteria and Saccharomycetes differ from 

 ordinary plants in a most important respect, 

 viz., that there is a complete absence of 

 sexuality and the reproduction is purely 

 vegetative. There are a few botanists, to 

 be sure, who think that there is a form of 

 sexuality in Saccharomycetes, but botanical 

 opinion at present is so overwhelmingly on 

 the other side that to call the question an 

 open one would require an explanation 

 which time will not permit. It may be 

 urged that in plants in which sexuality is 



