8 MORPHOLOGIC VARIATION 



life cycles of bacteria. He recognizes two cycles, a minor one con- 

 sisting of a single generation, i.e., the changes involved in the devel- 

 opment of a cell from one division to the next, and a major one con- 

 sisting of the regular changes occurring during the growth and aging 

 of a culture. This conception was developed from observations of 

 morphologic variations of an organism isolated from beer, Pseudo- 

 monas cerevisice. The young forms are motile rods; with increasing 

 age of the culture these tend to lose their motility and to form 

 chains; with still greater age certain of them become swollen at one 

 end and accumulate numerous metachromatic granules. These lat- 

 ter dauerjormen are the more resistant to various agents than are the 

 young cells, but not as resistant as the endospores of spore-forming 

 bacteria. With the latter the endospore formation occupies the same 

 stage of the major cycle as do the dauerjormen of the beer organ- 

 ism. When the latter are transferred to fresh media they rupture 

 and discharge several small cells which immediately develop into 

 motile rods. He is rather inclined to believe that the metachro- 

 matically stained granules of the dauerjormen are of a nuclear nature, 

 and that the schwdrmer develop from them. 



Fuhrmann lays considerable stress upon the regularity with which 

 the various changes in morphology occur in succession during the 

 aging of a culture. Various external factors tend to influence this 

 cyclical development only in degree. The age of the culture seems 

 to be the most important factor. To this extent his ideas anticipate 

 somewhat and are in agreement with my own. His papers have only 

 come to my attention during the preparation of this manuscript. 



While in most of these papers no exact details of the nature and 

 sequence of the supposed life cycles are given, and the various authors 

 are not in perfect agreement on all points, the same general idea 

 clearly runs through all of their writings. This idea has perhaps been 

 most clearly formulated by Mellon, who states that "bacteria in 

 their fundamental biology are in reality fungi that have been tele- 

 scoped down, as it were, to a somwhat lower order; but this order 

 is not so low as to preclude the preservation by the bacteria of the 

 fundamental organization characterizing the fungi and higher plants. 

 .... In point of fact, instead of reproducing themselves by transverse 

 fission alone, we know that under conditions none too specialized 



