CYTOMORPHOSIS IN BACTERIA 141 



the case of the cholera vibrio, which may perhaps be taken as a 

 type of the spiral organisms, the embryonic forms are characterized 

 particularly by straightness of their cells; they are bacillarly in form. 



The mature or differentiated forms, beginning to develop with 

 negative acceleration in growth and reaching their maximum at the 

 end of growth, are just the reverse of the embryonic forms in the 

 characters enumerated above; in most species the cells are shorter 

 and more nearly approach the oval or spherical form; they are 

 less variable in size, more variable in form. In the diphtheriod 

 group they are longer and more slender. With the cholera vibrio 

 they are particularly characterized by curvature of the cells. In 

 all forms they are less deeply stained by the basic dyes. It is of 

 course obvious that these cells are not differentiated in the sense that 

 different cells show a great diversity of form and internal structure 

 as occurs in the differentiated cells of a multicellular organism; 

 such cannot be the case because the cells are all contained in the 

 same environment which must be nearly uniform throughout. But 

 the individual cells do show a differentiation in their internal struc- 

 ture, many forms developing within the protoplasm spores or granules 

 of one type or another, especially volutin. Now it is just this 

 development of internal "paraplasmatic" structures which charac- 

 terize the differentiated cells of a multicellular organism, and which 

 are either the result or the cause of their diversified function. In 

 this sense at least, then, there does occur differentiation in the 

 mature cells of bacteria. 



The senescent forms begin to develop with the initiation of the 

 death phase. Perhaps because the data are too incomplete their 

 relationship to this phase of growth is not so clear as in the case 

 of the other two cell types; but it would seem that they are not so 

 definitely associated with the rate of death as with the rate of 

 autolysis during the death phase. They are characterized by in- 

 creased variation in form of cells and especially by an increasing 

 proportion of asymmetrical cells. I have already suggested that 

 this is due to the action of some agent upon the cell wall. These 

 senescent forms are also characterized by still less affinity for the 

 basic dyes and finally by the development of an affinity for the 

 acid dyes. 



