CHAPTER X 



ON CYTOMORPHOSIS IN BACTERIA 



The collection of these data has proven exceedingly tedious 

 and time-consuming. The observations recorded in the preceding 

 pages have required measurements of one character or another of 

 nearly 100,000 cells. For this reason the data are quite incomplete. 

 Much more work will have to be done, many more species of bac- 

 teria will have to be studied on a greater variety of media, before 

 the nature and significance of their morphologic variations can be 

 clearly understood in all details. But enough has been presented, 

 I believe, to indicate clearly that the problem includes factors not 

 recognized by either monomorphists or pleomorphists. The cells of 

 bacteria do vary in size and form and internal structure, but these 

 variations occur in a very regular and orderly fashion; they can be 

 measured, and the quantities obtained by such measurement when 

 plotted form regular curves. These variations are not confined to 

 the late stages of growth but occur continually through all stages. 

 Each character reaches its maximum development in some particular 

 phase or at some particular point of inflection of the growth curve. 

 Those factors which cause a variation in the growth rate equally 

 vary the rate and degree of change in morphologic characters. The 

 morphologic variations of bacteria are therefore an expression of 

 the variations in growth rate. 



The character of these morphologic variations in the early stages 

 of growth depends largely upon the age of the cells used for seeding. 

 If these were embroyonic forms rapidly growing, they continue as 

 such in the new medium. If, however, they were of a later stage 

 of development, they may remain dormant for a time and even 

 continue to change in the same direction as in the old culture from 

 which they came. Thus in Cultures II and III of B. megatherium 

 described in Chapter IV, the cells decreased slightly in size during 

 the first hour of growth; with the diphtheriod organism recorded in 

 Chapter VI there was an initial increase in size; with the cholera 



139 



