Ill CHARACTER OF BACILLUS 29 



excess of those that are possessed of motility ; the 

 number of these latter being limited. In prepara- 

 tions made of recent culture, except potato or broth 

 cultures, the number of motile forms is appreciably 

 greater than from a culture of some days' standing ; 

 in older cultures they are missed. If of any gela- 

 tine cultivation, say a streak culture or a plate cul- 

 ture, fresh preparations are examined from day to 

 day, the same tube or the same colony being used, 

 it is noticed that while in the first few days the 

 number of motile bacteria is sufficiently great to 

 see in every field several or even many examples, 

 about the end of the week, and later, few motile 

 forms are to be found in the whole slide. And if 

 now fresh sub-cultures are started, it is again noticed 

 that, while recent, they show the motile forms fairly 

 abundant ; if of some standing, only non-motile ones 

 are present. I conclude from this that there is 

 produced in the cultures, by the growth, a chemical 

 substance which inhibits and is adverse to the 

 motility. It cannot, I think, be explained by saying 

 that the later offsprings are devoid of the organs 

 of motility, i.e. the flagella, while the earlier off- 

 springs possess them, because when they are planted 

 on fresh nutritive medium they again show motility, 

 and on potato or broth, even after 24 hours' growth 

 no motile forms are found. It can hardly be said 



