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early separation of the Gram-negative and the Gram-positive cocci, 

 which ultimately leads to the creation of the new Gram-negative genus 

 Veillonella which is the counterpart of the Gram-positive genus Micro- 

 coccus. In consequence of this the final system has the great merit of a 

 logical and consistent structure. It should, however, be questioned 

 whether it is commendable to restrict the physiological characters to 

 specific delimitation. We can agree with the author that 'aerobic' and 

 'anaerobic' mode of life as based solely on the sensitivity of the organ- 

 ism towards free oxygen is a rather dangerous character. Yet it seems 

 to us that the katabolic nature of the organism is a much more essen- 

 tial property and should not have been left out of consideration in the 

 demarcation of higher groups than species. For it can hardly be 

 doubted that the relationship between aerobic Micrococcus species and 

 aerobic Sarcina species is at least as close as that between the latter and 

 the anaerobic Sarcina species such as Zymosarcina ventriculi (Goodsir) 

 Smit [Smit, 1930]. 



4. OUTLINE OF A RATIONAL SYSTEM FOR BACTERIAL CLASSIFICATION 

 ON THE BASIS OF OUR PRESENT KNOWLEDGE 



The preceding pages have not only served the purpose of exposing 

 the manifold weaknesses and inconsistencies of the more recent systems, 

 they may also perform the function of illustrating the considerations 

 to which the general principles laid down in Section 2 lead in con- 

 crete instances. Therefore in the following attempt at sketching an 

 outline of a rational bacterial system we shall also draw upon material 

 which has already been used in the discussion of our attitude towards 

 previous classifications. 



It may be recalled that in the foregoing we have had the opport- 

 unity to point out that the assumption of both a morphological and a 

 physiological evolution seems justified. A true reconstruction of the 

 course of evolution is the ideal of every taxonomist. But, as has been 

 rightly emphasized by Pringsheim, such a reconstruction is not feas- 

 ible, firstly because the accepted relationships remain conjectural, and 

 secondly because a number of the connecting links will be missing in 

 the bacterial kingdom as it exists to-day. With Pringsheim we are of 

 the opinion that 'ein wirklich wissenschaftliches System, das also mit 

 Kritik aufgestellt ware, gar nichts anderes tun konnte, als zu ver- 



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