8 RELATIONSHIPS OF THE COCCACEjE 



tinuous variations," and held that the latter at least 

 were positively inheritable. 



The appearance of "sports" or mutations in bacterial 

 cultures has been recorded by a number of observers; 

 but such observations must be scrutinized with care 

 in view of the ever present danger of contamination. 

 Neumann (1897) records the sudden appearance of 

 sharply marked color varieties, as sectors in old and care- 

 fully sealed stab cultures of staphylococci. Beyerinck 

 (1900), working with three distinct organisms allied to 

 B. prodigiosus, observed the appearance of colorless 

 races in each strain, the other properties of the 

 stocks remaining unaltered. In cultures of Photo- 

 bacterium indicum the same investigator noted the occur- 

 rence of two distinct mutations. In both cases the loss 

 of normal characters was involved, and not the devel- 

 opment of new powers. A somewhat more striking 

 observation was communicated by Neisser (1906) to a 

 local bacteriological society in 1906 and later pub- 

 lished in greater detail by Massini (1907). The parent 

 strain in this case was a bacillus of the paratyphoid 

 group which never fermented lactose and therefore 

 produced only colorless colonies on Endo's medium. 

 After several days' development raised nodules appeared 

 in the colonies. If plates were sown before these devel- 

 oped, all the daughter colonies were again colorless; 

 but if plates were sown from a nodule in a colony 

 three or four days old, two sorts of daughter colonies 



