INFLUENCE OF TEMPERATURE. 



393 



hours then reveals only chains of short rods. We have thus induced 

 a reversion to the original forms of cell, and have thereby learned 

 the morphological influence of temperature. Of course, neither 

 the composition of the nutrient medium nor the condition of 

 the seed is a matter of indifference. Thus, for instance, if, 

 instead of sowing the young cells presupposed in the foregoing 

 demonstration, those already forty-eight hours old are employed, 

 then the conversion into long threads becomes very difficult. 

 In the case of lager-beer the development proceeds somewhat 



FIG. 89. Bacterium aceti. 



Lou;; threads. Culture twenty-four hours old in " doppel-bier " at 4o-4o.5 C, In several 

 places the breadth of the threads is exaggerated. Magn. 1000. (After Hansen.) 



differently to that occurring in the "doppel-bier" hitherto 

 mentioned. 



Bacterium aceti and B. Kutzingianum behave very similarly 

 under the circumstances now in question. A few small differ- 

 ences are, however, unmistakably evident. Thus, for instance, 

 in harmony with the plumper form of the short rods of B. Pas- 

 teurianum, the breadth of its long threads is also greater, as will 

 be evident on reference to Figs. 85 and 89 ; the long threads of 

 B. aceti are thinner, but attain a greater length, viz., up to 500 u.. 

 On the other hand, the long threads of B. Kutzingianum are con- 

 siderably smaller than those of the other species. Finally, it 



