Feb. io, 1923 
Life History of Azotobacter 
429 
Lohnis et Pillai and Bacillus danicus Lohnis et Westermann; those 
grown from A. agile showed some marks of Bacillus silvaticus A. M. et 
Neide, which, however, is closely related to Bacillus luteus. All cell 
types were transformed into each other. 
The reproductive organs of Azotobacter are (1) gonidia, in part filter¬ 
able, produced in small numbers, one to four, in the small cells, and in 
larger quantities in the large ones, which act in this case as gonidangia; 
(2) regenerative bodies and exospores, either produced by the cells in 
lateral or in terminal position, or growing up from the symplasm; (3) 
arthrospores, formed by fragmentation of the rod-like or fungoid cells; 
(4) microcysts, that is, small or large globular or oval resting cells; (5) 
endospores, produced singly by the rod-like cells in terminal or in central 
position, or to two or more in globular or spindle-shaped sporangia. 
Gonidia form the basis for the development of regenerative bodies, 
arthrospores and endospores; the production of polar regenerative 
bodies always preceded the establishment of endosporulation, and endo¬ 
spores were found to be able to reproduce gonidia and regenerative bodies. 
The formation of the symplasm and the regeneration of new cells 
from this more or less amorphous substance of varying stainability 
proceeds with Azotobacter in the same manner as with all other bacteria. 
Amoeboid movement of symplasm was never observed, but strong inner 
movements were seen, and occasionally globular macrocysts were found 
which are analogous to the macroplasts discovered by Lankester. Be¬ 
sides normal cells, relatively solid agglomerations of more or less irregular 
shape were produced by the symplasm, so-called sclerotia, which later 
either transformed themselves to vegetative or reproductive cells or 
reentered the symplastic stage. Large “filidia,” representing another 
type of more or less irregular and ephemeric upgrowth from the sym¬ 
plasm, were also observed. 
Conjunction was regularly seen in young cultures before the formation 
of gonidia, regenerative bodies, and of exospores and endospores took 
place. Part of the regenerative bodies are clearly zygospores. The 
cell union is either temporary, effected by connecting beaks, bridges, or 
by direct contact of two or more cells, or permanent due either to a 
sticking together of two uniform cells, which retain their identity, or to 
a coalescence of two cells of more or less different appearance. These 
various modes of conjunction, observed with Azotobacter as with other 
bacteria, resemble very closely those recorded with yeasts and with 
protozoa. 
The fact that the different developmental stages of Azotobacter could 
be in part identified with certain so-called species belonging to the 
form genera Micrococcus, Bacterium, Pseudomonas, Bacillus, and Myco¬ 
bacterium demonstrates anew and conclusively that the whole system 
of bacteria needs complete revision, which is to be based upon the 
results of thorough examination of the life histories of the bacteria. 
Some bacteriologists will be inclined to explain the phenomena re¬ 
ported in this paper by assuming accidental contaminations of the cul¬ 
tures studied. However, careful consideration of the data reported 
will show that most of the changes shown can not reasonably be ex¬ 
plained upon the hypothesis of contaminations and that there are no 
changes reported where the reasons that might be imagined for the 
adoption of the contamination hypothesis deserve any more considera¬ 
tion than the reasons advanced for considering them to be normal changes 
in the life cycle of Azotobacter. 
