Feb. xo, 1913 
Life History of Azotobacter 
427 
cation of Bacterial Types (45) that Azotobacter does not produce heat- 
resistant endospores. As an analogous assertion had been made by 
this Committee in a preliminary report, the senior author pointed out 
at the Annual Meeting of the Society in 1917 that this opinion was con¬ 
trary to the facts recorded by him in 1914 and 1916 ( 26 , 28). The 
final report of the committee, however, still retains the statement that 
Azotobacter does not produce heat-resistant spores. Jones’ assertion 
is in conflict with our observations and, furthermore, seems to be con¬ 
tradicted by his own data. He reports (16, p. 328) that some of his 
stock cultures— 
produced colonies of encapsulated spore-forming rods both large and small. 
Because these sporulating rods did not grow like Azotobacter, he con¬ 
cluded that they were contaminations. That this assumption may 
have been correct is of course possible, but it is equally possible that the 
facts observed are further proof that endosporulating rods may be 
produced by Azotobacter. We tried to make it clear in our first paper 
on this subject (26) that naturally the sporulating cells of Azotobacter 
differ in their growth as in their appearance more or less from the non- 
sporulating cells, but that the possibility to change them back to the 
original nonsporulating form proves beyond doubt that they are really 
a type of growth of Azotobacter and no “contamination.” To assume 
that morphologically different cells should display the same physiological 
(cultural) character is, of course, quite illogical. This point was em¬ 
phasized in the following statement in our preliminary paper ( 28 , p.690): 
Such wide morphological differences must always be connected with no less con¬ 
siderable alterations of the whole physiological character, so that these other types, if 
they are known, of course, are stored away as entirely different “ species' ’ in various 
remote places in the so-called “system” of bacteria. This conclusion can be drawn 
with absolute certainty from our observations on B. azotobacter as well as from Henri's 
experiments with B. anthracis . If only those changed forms, frequently seen in all 
bacteriological laboratories, had not been persistently discarded as uninteresting 
“involution forms” or as “contaminations,” the whole situation would undoubtedly 
be much clearer and much more satisfactory. 
Transformations from and to the original type of growth alone are 
decisive. That they can not be expected in short-termed experiments 
conducted along the customary lines of bacteriological research is amply 
proved by the facts recorded in this and in the first part of our Studies 
upon the Life Cycles of the Bacteria (25). Negative results based upon 
such experiments are not conclusive. 
With reference to the question of conjunction of bacterial cells, Jones 
07 > P- 330) states— 
that what is here referred to as conjunction of two individual cells is rather the incom¬ 
plete fission of individual cells in process of division. 
That there were “side connections” which drew our attention to this 
point, and that these lateral bridges are clearly visible in our photographs 
can not be explained, however, upon the assumption of incomplete 
fission. That also in this case we merely rediscovered a fact which 
should long have found its place in the bacteriological text books was 
shown beyond doubt by the data we were able to collect and to present 
in Part I (25, p. 197-204). 
That pathogenic bacteria—for example, the causative agents of bubonic 
plague, anthrax, cholera, diphtheria, etc.—are just as pleomorphous as 
Azotobacter, Nitrosomonas, Bacterium radicicola , etc., and that their 
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