39 



It is remarkable that the transformation in this phosphorescent bactery sometimes 

 suddenly ceases and is replaced by a process of variation where, beside a completely 

 dark form (the variant), the phosphorescent form with the full primitive phos- 

 phorescent power again springs up. This is not the same as common atavism, where 

 the stock which throws off the atavist does not change further, but it is probably 

 comparable to the splitting of a bastard into the two components. Very slow cell- 

 partition, caused for instance by culture at a low temperature, furthers this pheno- 

 menon. On the other hand, the cause of the transformation may be a too rapid 

 process of cellpartition in which the photoplasm, which seems to grow more slowly 

 than the rest of the protoplasm, remains behind in its development. 



In another phosporescent bactery of the sea, common on our coast, Ph. hollandiae, 

 I hitherto only saw transformation, so that this species quickly disappears from the 

 cultures as a phosphorescent bactery. 



In a pigment bactery (Bacillus viridis) I saw, apparently without any other 

 change, the at first very strong power of liquefying gelatin, by and by get lost in all 

 the individuals. 



On the other hand, I have seen in some vibrions, in a corresponding way, from 

 non-gelatin-liquefying individuals come forth liquefying ones. 



The new forms, thus called into life give, at superficial examination, quite the 

 impression of new constant species. They cannot, however, be valued as such as they 

 differ only by one or very few characteristics from the mother forms. This is the 

 cause why they must be classified as variants, quite like those of the following case. 



3. Common variation. 



The third and most frequent form of variability is common variation. Here the 

 normal form continues unchanged, but now and then throws off individuals, the 

 variants, which, from the beginning, are likewise constant and remain so, but which 

 every now and then again throw off other variants, among which the normal form may 

 occur as an atavist. These variants probably correspond with many well-known so- 

 called varieties or races of culture plants and domestic animals, and likewise, I should 

 think, with the interesting new forms obtained by Prof, de Vries from Oenothera 

 lamarckiana 1 }. They remind us in some respects also of the Pleomorphy in the 

 Fungi, which especially in the Ustilaginae, can easily be observed in the laboratories 

 and about which, in particular Brefeld, has made many researches 2 ). 



The names variant and sub-variant I have chosen, because in the here discussed 

 products of hereditary variation, which differ apparently very much, but in fact only 

 little from the normal form, I think to see the lowest degrees of the natural system 

 following above the individual, and to them are given those names according to the 

 rules of botanic nomenclature 3 ). 



') These Proceedings. Meeting of 29 Sept. 1900 pag. 246. Comptes rendus. T. 131 

 pag. 124 en 561, 1900. 



s ) Botanische Untersuchungen iiber Hefenpilzc. Heft 5. 1883. 



') A. De Candolle, Lois de la nomenclature botanique, 2e Ed. pag. 15, 1867, and 

 Nouvelles remarques, pag. 48 and 63, 1883. 



