36 KANSAS UNIVERSITY SCIENCE BULLETIN. 



rent type under parallel conditions resulted in a comparatively 

 actively motile culture. 



Partial loss of motility is a not uncommon phenomenon 

 in the Colon group of bacteria, and is often the immediate 

 result of the environment. But the observations described 

 above cannot be all explained as the result of conditions of 

 growth ; for the non-motile strains apparently appeared sud- 

 denly, and remained non-motile through many generations 

 and under a great variety of conditions ; and it seems more 

 probable that we have to do with variations somewhat simi- 

 lar ill character to those of race A. But the non-motile types 

 seem less stable and more easily influenced by selection than 

 the type varying morphologically, and it is probable that 

 such non-motile types will in time revert to the parent stock 

 unless kept up by occasional selection. 



SUMMARY OF EXPERIMENTS ON COLI COMMUNIS. 



1. Variations arise in Bacillus coli communis, which, like 

 those of Saccharomyces anom,aliis, may give rise to races exhibit- 

 ing permanent morphological characteristics not possessed by 

 the type. 



2. These variations arise suddenly and apparently inde- 

 pendently of conditions of cultivation ; and are to be com- 

 pared with mutants observed in higher plants. 



3. They show, in general, a tendency to diminished rapidity 

 of growth at the beginning, but, having once begun to de- 

 velop, they produce as a rule cultures as vigorous as the nor- 

 mal. 



4. They are of different types, and the new races arising 

 from them may be characterized by an abnormal tendency to 

 produce long filaments, or by a nearly complete loss of 

 motility. 



5. These new races vary in the degree of their deviation 

 from the type and in their stability. While some apparently 

 require more than one selection to preserve their fixity, others 

 have been constant from the first selection over a period of 

 two years and eight months. 



6. One new race further differs from the type in exhibiting 

 an increasing power of fermenting sugars, and a partial loss 

 of sensitiveness to agglutinating serums. 



