PREFACE 



without having recourse to their morphologic characters, and the 

 carrying on of many types of bacteriological investigation without 

 ever using the microscope. 



In this work I shall show that, contrary to the orthodox teach- 

 ing, the cells of bacteria are constantly changing in size and form and 

 structure ; but that instead of these changes occurring in a haphazard 

 or meaningless fashion, or instead of being phases in a rather vague 

 and complex life cycle, they occur with great regularity and are 

 governed by relatively simple laws which, after more data have 

 been accumulated and analyzed, may probably be very precisely 

 formulated. 



Bacteria have been rather neglected by the general biologists, and 

 in works on general biology one rather gains the impression that 

 bacteria are to an extent organisms apart from the rest of the living 

 world, more or less exceptions to the general biologic laws. This is 

 due in part to the fact that the study of bacteria requires a peculiar 

 technique, but more particularly to the fact that they are so minute 

 in size and simple in form. There is no multiplicity of structures 

 to explain the complexity of function; their very simplicity has re- 

 pelled rather than invited research. More particularly the absence 

 of a demonstrable nucleus and of sexual reproduction has discouraged 

 investigation. Now this would seem on the face of it illogical; the 

 simplest forms of life should be studied before the complex. Here 

 are the most elemental organisms that can be visually observed, yet 

 we know practically nothing concerning their fundamental biology. 



My investigations indicate that the growth of bacteria in artifi- 

 cial cultures is governed by the same laws as govern the develop- 

 ment of a multicellular organism; that their cells during growth pass 

 through exactly the same sort of a developmental cycle as the cells 

 of a plant or animal, exhibiting in turn an embryonic form during the 

 period of rapid growth, a mature or differentiated form during the 

 period of slow growth or rest, and a senescent form during the pe- 

 riod of death; that in short we may speak of a "cytomorphosis" in 

 populations of free unicellular organisms differing only in degree 

 from that of muticellular individuals. If this hypothesis be accepted 

 it must prove of great importance in general biology, for it carries 

 with it the implication that multicellular organisms are after all but 



