862 A YELLOW EACE OF BACILLUS PSEUDARABINUS, &c. 



have already shown that Bac. levaniformans exists as white and 

 as yellow races, and that the latter change to the former in the 

 laboratory. 



Change of colour is therefore not uncommon, but permanent 

 differences in colour production by the same organism are not so 

 frequently found. Perhaps the best known examples are to be 

 found among the micrococci. The pus-forming Micrococcus 

 pyogenes, (Rosenberg) Mig., is recognised as probably being a 

 permanently white race of Micrococcus aureus, (Rosenberg) Mig. 

 The white and yellow races of Bac. pseudarahlnus were obtained 

 as such, and they have preserved their respective colours for a 

 year under laboratory conditions. 



