146 MORPHOLOGIC VARIATION 



fast line, between populations of one-celled organisms and multi- 

 cellular individuals; that a higher plant or animal is but a popula- 

 tion of more highly differentiated cells. But there has been, in the 

 past at least, a tendency to look upon cell differentiation in multi- 

 cellular organisms as being the result of some organizing agency 

 peculiar to such individuals. If, however, we find in cultures of 

 microorganisms where no such governing agency can be supposed 

 to exist, a differentiation of cells, even though very primitive, we 

 are forced to conclude that such is not the case; that the high degree 

 of organization of higher organisms is a result and not a cause of 

 the high degree of cell differentiation. 



This theory of cytomorphosis in bacteria is not entirely in dis- 

 agreement with the current theory of monomorphism, which has 

 always recognized two of the three cell types; the so-called normal 

 forms which I designate mature or differentiated, and the involution 

 forms which I call senescent. It differs markedly, however, in the 

 recognition of a third type, the embryonic cells characteristic of 

 the stage of accelerating growth which will probably be found in 

 all species of microorganisms; but just this recognition of the em- 

 bryonic forms is sufficient to upset the entire theory of monomor- 

 phism, for it implies that morphologic variations are occurring con- 

 tinuously at all stages of growth, rather than only during the period 

 when cultures are becoming aged and dying. It would seem, there- 

 fore, that the monomorphistic theory without modification can no 

 longer be considered sound. 



On the other hand, this theory of cytomorphosis is not necessarily 

 opposed to the theory of complex life cycles maintained by the 

 more recent pleomorphists. The two viewpoints are rather different 

 ways of looking at the same thing than are they mutually exclusive. 

 But with acceptance of the theory of cytomorphosis we are no longer 

 forced to explain every variation encountered as some sort of a mode 

 of reproduction other than simple cell division. Most of the cell 

 types described as extraordinary reproductive bodies by the pleomor- 

 phists, I have encountered only in the death phase, and their occur- 

 rence is apparently dependent on the rate of autolysis; it would 

 seem, therefore, more likely that they are cells which are undergoing 

 retrogressive changes than cells which are embarking upon some 



