DISSOCIATION AND TRANSFORMATION 165 



useful and logical. There is much to be said both for and against 

 Dawson's proposal and so it may be permissible to turn to one who 

 speaks with authority on this important subject of bacterial dis- 

 sociation. Hadley's opinion expressed in a letter written in 1933 to 

 Dawson was in part:* 



Making a decision regarding the proper course to pursue in changing 

 the nomenclature now employed for designating the phases of the pneu- 

 mococcus, in favor of the symbolization which your studies thus far 

 seem unquestionably to justify, might easily depend on how fully an in- 

 vestigator has in mind the details of dissociative variation as a phe- 

 nomenon observable in all bacterial species, and how clearly he can 

 perceive the parallel trends in such variations, — as opposed to a limited 

 outlook on the one species in which he may be especially interested. 



If bacteriology were limited to the study of a few species, or to the 

 Pneumococcus, it would make little difference what the observed phases 

 were called, because no generalizations would be involved, and the 

 phase symbols would possess no significance for bacteriology as a 

 whole. A, B and C, or X, Y and Z would serve the purpose. . . . 



The desirability of adjusting the difficulty in the Pneumococcus situa- 

 tion, and of doing it without delay, is the more to be recommended in 

 view of the increasingly wide recognition that the same or analogous 

 phases exist in numerous other species. The facts are now becoming so 

 extensive and well grounded that they are offering, for the first time in 

 the history of bacteriology, a basis for the formulation of general laws ; 

 and for making possible a certain kind of "predictability," as I have 

 perhaps already demonstrated to you. To this extent pure bacteriology 

 is beginning to take on the aspects of a real science — a compliment 

 which (to my mind) it has scarcely been appropriate to offer in the 

 past. 



To facilitate this highly gratifying trend it stands to reason that all 

 who work with the problems of variation should keep in mind the dual 

 significance of their results, and make possible a correlation of their 

 own results with those of others; also to make quick and decisive cor- 

 rections when such are clearly in order. To label as a smooth a Pneu- 

 mococcus phase that is demonstrated to be a mucoid, or to label as a 

 rough a phase that is clearly a smooth, may do little harm to those 



* The authors appreciate the courtesy of Doctors Hadley and Dawson in 

 granting permission to include portions of this letter here. 



