4 2 



existence of sub-variants proves that the great and sudden leaps, observed in the 

 variability everywhere in the vegetable and animal kingdoms, are no necessary of 

 variability. Furthermore these sub-variants prove that even slight deviations may be 

 in high degree hereditary-constant 1 ). 



5. Variation in Bacillus prodigiosus. 



This well-known red pigment-bactery is cultured by me in three distinct natural 

 varieties. One of them does not liquefy the culture-gelatin 2 ), of the two others 

 which do, one 3 ) has the power of causing various carbon-hydrates to ferment under 

 production of hydrogen, the other not 4 ). All three produce, in older cultures, a 

 variant which is completely colourless, but in all other respects possesses the properties 

 of the normal form whence it has taken birth, so that there are non-liquefying and 

 fermenting, and liquefying non-fermenting colourless variants. All these variants 

 have remained hereditary-constant in my experiments and produce no atavists like to 

 the mother form, i. e. red-coloured colonies. There is no doubt, but, if these variants 

 were met with in nature, not accompanied by the normal form from which they arise, 

 they would be taken for as many new species. Still it would be an error to admit them 

 as species into the system, as a more minute investigation shows that, except in the 

 power of forming /pigment, they correspond in all other respects with the normal 

 forms, and one single point of difference determines only a variant. 



I doubt by no means that B. prodigiosus can also vary in other directions; this 

 follows already from the fact that I could find three very different natural varieties, 

 which all produce' red pigment 5 ) But I have not taken pains to trace other variations. 



Sub-variants between the normal forms and the said colourless variants are, or 

 at least seem rarer than the main variants. They are rose-coloured and at colony- 

 selection almost as constant as the normal form. They also produce like the latter the 

 constant colourless main-variant, and moreover show a propensity for atavism. In 

 each natural variety I have found only one or two rose-coloured sub-variants. 



6. Variation in Photobacter indicuni. 



This phosphorescent bactery was isolated by Prof. Fischer of Kiel, from 

 seawater in the vicinity of the isle of Santa Cruz, one of the Antillies, on January 10, 

 1886. I received material of it in May 1887 and have without interruption cultured 

 it till now. Already in 1887 I perceived, that with the growing older of the cultures, 

 two main variants arise and even in so great a number that the normal form can be 



l ) For the more complicated phenomena of variation in some species of Saccharo- 

 myces, I refer to my paper Sur la regeneration des spores chez les levures etc., Ar- 

 chives Neerlandaises, Ser 2, T. 2, pag. 269, 1899. 



-) Isolated from potatoes grown hoi low in the soil and given me by Prof. Ri tzemaBos. 



8 ) Isolated from tubercles of red clover. 



4 ) Isolated from bones kept at the open air on the bone-hill of the gelatin- and 

 glue-factory at Delft. 



5 ) The red pigment of B. prodigiosus is a product of excretion found between the 

 living and partly accumulated in dead bacteria. It is in my opinion the product of 

 specific chromoplasm, which forms a small part of the protoplasm in general. 



