110 MORPHOLOGIC VARIATION 



to those used for seeding; they look like streptococci. This is rather 

 interesting because various authors, particularly Mellon, have sug- 

 gested that the diphtheroids and the streptococci are closely related. 

 If such a relationship exists, these observations might be construed 

 to indicate that the diphtheroids have developed from the strepto- 

 cocci and during their embryonic phase revert to the ancestral type. 

 At any rate it would seem likely that the so-called mutations of 

 diphtheroids to streptococci as described, among others, by Mellon, 

 may be the result of merely comparing different phases of growth, 

 a culture on one medium being in the resting phase when on another 

 it may still be actively growing. 



