136 THE MICROSCOPE. Sept. 



seen that at about the middle the cell-wall becomes drawn 

 in and soon a new wall is completely formed between 

 the two daughter cells, which in time become full grown 

 bacteria. 



The Rapidity of RErRODucTiON of Bacteria. — The 

 rapidity with which the cells may divide and thus repro- 

 duce themselves is marvelous; under the best of conditions 

 a single cell will divide once every half hour and it only 

 requires a little work in compound multijilication to show 

 that a single cell under these conditions will produce 

 in twenty -four hours 10,77*7,220 baby bacteria and at the 

 end of forty-eight hours the number will be 281,500,000,- 

 000,000. It is quite needless to say that the proper con- 

 ditions for this rapid development are not maintained in 

 nature for any length of time or the whole globe would 

 long ago have been completely overrun. 



Cell Grouping of Bacteria.— Bacteria may occur 

 singly or in groups and these groups are determined by 

 two factors, the direction in which the cell divides, and 

 the condition of the cell-wall. It will be noticed that 

 bacilli and spirilla always form their new walls in but a 

 single plane and that peri>endicular to the long axis, so 

 that these forms may be grouped in but a single way, in 

 the form of threads, varying in length according as the 

 condition of the cell-wall causes the individuals to adhere 

 or allows them to separate. As examples see Figure 2, 

 Nos. 6-9. In the coccus forms the plane of division may 

 take many directions. Where two individuals remain 

 attached they are called diplococci, Figure 2 (No. 1). 

 Arranged in chains (No. 2), they are streptococci. In 

 fours (No. 3) tetrads, Avhile No. 4 represents groups of 

 eight arranged in the form of packets and called sarcina. 



Conditions Necessary for the Gro\vtii of Bacteria. 

 — Bacteria, in common with the whole class of fungi, re- 

 quire that their carbon should be furnished them in the 



