20 



Lectures on Bacteria. 



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refringent power, its lustre and dark outline ; it assumes the ap- 

 pearance of a vegetative cell, and grows at the same time to the 

 size and shape of the vegetative cell from 

 which it sprang. With the completion 

 of this process movement begins in the 

 motile species, and this is followed by 

 the growth, division, and grouping which 

 have been described above as occur- 

 ring in the vegetative stages, and which 

 at length come to an end with a fresh 

 formation of spores. In many cases 

 a few hours only intervene between the 

 first observable commencement of ger- 

 mination and active vegetative growth. 

 See above, Fig. i, h-m. 



With the first increase in size a mem- 

 brane is often seen to split and rise from 

 off the surface of the growing cell, being 

 evidently lifted from off it by a swelling 

 gelatinous outer layer surrounding the new 

 membrane of the cell. The rent through 

 the membrane is in the direction of 

 the length, or across the middle, accord- 

 ing to the species. The former is the 

 case according to Prazmowski in Bacillus Amylobacter, and it 

 occurs also in other species. The latter has been observed in 



Fig. 2. A Bacillus Anthracis. Two filaments partly in an advanced 

 stage of spore- formation ; above them two ripe spores escaped from the 

 cells. From a culture on a microscope-slide in a solution of meat-extract. 

 The spores are drawn a little too narrow ; they are nearly as broad as the 

 breadth of the mother-cell. B Bacillus subtilis. I fragments of filaments 

 with ripe spores. 2 commencement of germination of spore ; the outer wall 

 torn transversely. 3 young rod projecting from the spore in the usual 

 transverse position. 4 germ-rods bent into the shape of a horse-shoe, one 

 afterwards with one extremity released. 5 germ-rods already grown to a 

 considerable size but with both extremities still fixed in the spore-membrane. 

 All magnified 600 times. 



Fig. 2. 



