July 31, 1916 



Life Cycles of the Bacteria 



683 



closely. However, similar difficulties occur in all such cases, where we 

 want to reach some clear ideas concerning the multitude of the varying 

 forms which we find in nature; and, as we now know that the life cycle of 

 the same bacterium presents so many more different aspects than we ever 

 expected before, we simply are compelled to take our refuge in some kind 

 of classification, however crude it may be. 



In Table I we give a summary of the different types of growth observed 

 thus far in our preliminary studies with 24 representatives of the group 

 of B. azotobacter. The laboratory numbers of the different cultures are 

 to be connected in the following manner with the different types of 

 Azotobacter, according to the denominations generally used : 



No. 1, 2, 10, 11, 12, 14, 17 to 20, Azotobacter chroococcum, old stock 

 cultures. 



No. 21 to 25, Azotobacter chroococcum, new cultures isolated from dif- 

 ferent soils. 



No. 3 to 6, 13 and 15, Azotobacter Beijerinkii. 



No. 7 and 16, Azotobacter vinelandii. 



No. 9, Azotobacter vitreum. 1 



Table I. — Types of growth observed with 24 cultures of Azotobacter 

 [The laboratory numbers of the cultures are given at the head of the columns] 



1 Another strain of A. rilreum isolated in 1904 in Leipzig bore the No. S (now missing) in our collection. 

 It died shortly before these investigations were started. One of the photographs (fig. 6 of Pi. A) was made 

 by using an old preparate of this culture. We hope to be able to replace it later by a new subculture of 

 the original strain left in the laboratory of the senior author ixi Leipzig. 



