158 TRANSFORMATION OF PNEUMOCOCCAL TYPES 



EXPLANATION OF PLATE 1 



The photograph was made by Mr. Joseph B. Haulenbeek. 



Fig. 1. Colonies of the R variant (R36A) derived from Pneumococcus Type II. 

 Plated on blood agar from a culture grown in serum broth in the absence of the 

 transforming substance. X3.5. 



Fig. 2. Colonies on blood agar of the same cells after induction of transformation 

 during growth in the same medium with the addition of active transforming prin- 

 ciple isolated from Type III pneumococci. The smooth, glistening, mucoid colonies 

 shown are characteristic of Pneumococcus Type III and readily distinguishable from 

 the small, rough colonies of the parent R strain illustrated in Fig. 1. X3.5. 



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