40 



Regarding the divisions above the species, de Candolle does not think it necessary 

 to give definitions, in which I quite agree with him. But singularly enough he does 

 try to do it for the ranks beneath the species, where he takes the greater or lesser 

 constancy at sowing as a criterion for the differences. This is not logical, here too, 

 definitions are unnecessary. 



Probably various causes give rise to the production of variants. Lengthened 

 growth at insufficient nutrition, and the prolonged action of the own secretion pro- 

 ducts of the microbes may, with some probability, be considered as such causes. 



The variant seems seldom, perhaps never, by one single cell-partition to result 

 from the mother-form, but only after some intermediary partitions, rapidly accom- 

 plished. With these latter partitions correspond the sub-variants, with a disposition for 

 atavism or further variation, and only keepable by colony-selection. 



I will now describe some instances of common variation ; first a few cases of the 

 originating of hereditary-constant variants, which seem unable to return to the 

 stock, then the more complicated case of constant and variable variants, among which 

 some with a great disposition for atavism, which case I have nearer investigated in 

 the West-Indian phosphorescent bactery and its relatives. 



I might augment these instances with many more, for most of the microbes with which 

 T occupied myself for a length of time, produced in my cultures more or less hereditary- 

 constant variants. Extremely variable are the mycelia of the Fungi, for which I refer 

 to the complicated relations of the aethyl-acetate-yeast, which I described and de- 

 monstrated in 1895 *)> an d where transformation and common variation both occur. 



4. Variation in Schizosaccharomyces octosporus*}. 



This curious maltose-yeast I detected in 1893 on dried orient-fruits as currants, 

 dates, raisins, and figs. I found a good method to separate this species from the other 

 microbes, by which it is possible as often as desired to bring it from nature into culture. 

 It proved to be a generally spread organism, which is found in Greece, Turkey, 

 Italy, Asia Minor and Java in one and the same variety. After many isolations I 

 found in 1897 3 ) a new variety on dates from N. -Africa. The culture is effected in 

 the like way as of beer-yeast on wort-gelatin. Maltose, like glucose and levulose, 

 undergoes a vigorous alcoholic fermentation, cane-sugar not at all. 



As well the usual form as the new variety produce 8-spored sporangia, the spores 

 of which colour intensely blue with iodium. During the growing a small quantity of 

 diastase is secreted. The vegetative condition which precedes the spore-formation, as 

 also the vegetative variant, which produces no more spores, of which more below, 

 multiply by partition (not as in other yeasts by budding) and colour yellow by iodium; 

 glycogene wants completely in it. Accordingly it is possible, by treating a culture 

 with iodium, from thousands of colonies, instantly to recognise those containing 

 spores, and from the intensity of the blue-colouring with some certainty to make out 



') Handelingen van het 5e Natuur-en Geneesk. Congres te Amsterdam pag. 301, 1895. 



-) Centralblatt fur Bacteriologie Bd. 16 pag. 49, 1894 and Ibid. Abth. 2. Bd. 3 pag. 

 449, 1897. In 1897 I put the variant on a level with a vegetative race, but as I now 

 think, in doing so I rated its systematic value too high. 



8 ) Together with a new quite different species of Schizosaccharomyces. 



