i6 



Lectures on Bacteria. 



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are known, are essentially the same in both, and they have now 

 to be described in detail in the case of Bacillus. See Fig. i. 



The Bacilli in the highest state of vegetative development are 

 rod-shaped or shortly cylindrical cells with the characters already 

 described, which either remain isolated or are united together into 

 unicellular rods or longer filaments; they are motile or motion- 

 less, and display active growth and division (Fig. i, a-c). 

 Both growth and division at length come to an end, and then 

 begins the formation of peculiar organs of reproduction — spores. 

 This process begins at the point to which it has been followed 

 furthest back with the appearance of a comparatively very minute 

 point-like granule in the protoplasm of a hitherto vegetative 

 cell. This granule increases in volume and soon presents the 



appearance of an elon- 



gated or round, highly 

 refringent, sharply-defined 

 body, which attains its 

 ultimate size rapidly, some- 

 times in a few hours, and 

 is then the mature spore 

 (Fig. I, d-f). The spore 

 always remains smaller 

 than its mother-cell, the 

 protoplasm and other con- 

 tents of which disappear 

 with the growth of the 

 spore, being doubtless 

 consumed for its benefit, until at length the spore is seen sus- 

 pended in a pellucid substance inside the delicate membrane 

 of the mother-cell (Fig. i, r, h^. 



Fig. I. Bacillus Megaterium. a outline sketch of a chain of rods in 

 active vegetation and motion, b pair of rods in active vegetation and 

 motion, p a 4-celled rod in this stage after treatment with alcoholic solution 

 of iodine, c 5-celled rod in the first stage of preparation for forming spores. 

 d-f successive states of a spore-forming pair of rods, d about 2 o'clock 



