148 



lost sight of, and a perusal of BEijERiNCKandvANDELDEN's studycan 

 be recommended to any microbiologist. 



It may finally be remarked that the question of the systematic 

 relationships of Bacillus oligocarhophilus , on which point some very 

 fallacious views have been ventilated in the literature, is greatly in 

 need of reconsideration. 



q. Studies on microbial variation i). 



Such a keen observer as Beijerinck was could not have failed to 

 be struck — even very early in his career — by the phenomena of 

 variation occurring with the various microbes which he studied in 

 detail. As might therefore be expected, the places in Beijerinck's 

 papers in which he refers to such variations are numerous. This 

 review will, however, be restricted to those publications in which 

 Beijerinck makes an attempt to collect and to co-ordinate his 

 various experiences in this field. 



We may start with the lecture which Beijerinck held in the meet- 

 ing of the Koninklijke Akademie van Wetenschappen of Amsterdam 

 on October 27th, 1900 2). The lecture was, as stated by Beijerinck 

 himself , a direct consequence of the f act that a month bef ore HuGO de 

 Vries at the same place had dealt with the origin of new forms in 

 higher plants in a lecture which brought a first outline of his well- 

 known mutation theory. 



In the introduction Beijerinck expounds the advantages which 

 micro-organisms offer f or the investigation of the laws of heredity and 

 variability, but it has to be acknowledged that nowadays it is difficult 

 to subscribe to several of his arguments. 



On proceeding to the subject proper — the different forms of 

 hereditary variation of microbes — Beijerinck makes a plea for his 

 view that mainly three types of variation should be distinguished, i.e., 

 degeneration, transformation and "common" variation. 



The term "degeneration" applies to the case that a freshly isolated 

 culture — initially growing abundantly — gradually and successively 

 loses, various properties this process finally leading to a complete loss 

 of reproductive power. The bacterium of "long whey", Streptococcus 

 hollandiae, which on cultivation rapidly loses its ability of slime pro- 

 duction, and which on prolonged cultivation quite regularly dies off, 

 is offered as an example. 



The word "transformation" is used in those cases in which all 

 individual cells present in a culture undergo a common change — 

 usually a loss — in properties. The loss of luminescence regularly oc- 



i) The reader is also referred to the interesting survey of J. J. van Loghem, Beije- 

 rinck en de kennis der bacterieele veranderlijkheid (Ned. Tijdschr. v. Geneesk. 75, 

 1046, 1931). 



2) Proc. Kon. Akad. v. Wet. Amsterdam 3, 352, 1900; Arch. néerl. d. sciences ex- 

 actes et naturelles Sér. II, 4, 213, 1901. 



