268 S. ORLA-JENSEN 



we knew only the few parasitic species and tried to group all 

 other animals and plants with them. The pathogenic bacteria 

 are, fortunately, in the minority; the bulk of bacteria are leading 

 a saprophytic existence and like the plants have their natural 

 habitats in the soil. We therefore first have to put in order the 

 saprophjrtes; then we can begin to mediate about where we have 

 to place the parasites. 



From the point of view here maintained I cannot follow Wins- 

 low in distributing the cocci firstly under the two groups para- 

 sites and saprophytes, and it seems to me that he is going rather 

 too far when he uses the chromogenic property of the cocci to 

 divide them into several genera. The formation of coloring 

 matter can on an extreme estimate, and only when taken together 

 with other characters, be adopted as a specific character; it 

 is too variable to be used as a generic character. We must at 

 times submit to being in doubt about what we are to call a 

 species and what we are to regard as a variety; but the generic 

 characters should be in some measure fixed, even though we 

 must admit that the many transitional forms between the genera 

 make it impossible to draw quite well-defined fines. 



On the other hand, I have confirmed the correctness of the 

 observation of Winslow that acid-forming cocci are always 

 Gram-positive, w^hilst the non-acid-forming are, as a rule. Gram- 

 negative, and consequently it is doubtless right on that basis to 

 set up two groups of cocci, which — I suppose — belong in quite 

 different places in the bacterial system. However, my two 

 groups of cocci do not cover those of Winslow, as I befieve I 

 am warranted in separating the lactic acid-forming streptococci, 

 and grouping them together with the rod-formed lactic acid 

 bacteria. The acid-forming micrococci and sarcinse I have 

 brought together in the genus Tetracoccus, as I believe it to be 

 quite as wrong to draw a hmit between the micrococci and the 

 sarcinae as between the short- and long-chained streptococci. 

 The property of cohering after division, though in a certain 

 measure characteristic of the bacteria, is to a great extent influ- 

 enced by the temperature and the composition of the nutritive 

 matter. For the Gram-negative, non-acid-forming or, at most, 



