EXPERIMENT STATION BULLETINS 



219 



Diplococcns. 



Tetrad. 



Sarcine. 



8treptococca3. 



Staphylo- 

 cuccaa. 



O 



f^ 



Fig. 8. 

 Diplucocci. 



Ufi 



Fig. 9. Tetrads. 



ZoOglea. 



alone, separated from others, but when 

 united in pairs, they are called diplo- 

 cocci. Groups of fours are also quite 

 common and to these groups the name, 

 tetrads, is given. Another arrange- 

 ment is where several of these tetrads 

 are arranged and brought together so 

 as to form a cube. These cube-like masses are 

 snrcines. If micrococci are arranged together so that one fol- 

 lows the other in a line, they will have the appearance of a 

 chain or a string of 

 '^l" beads. Cocci so joined 

 i* are known as streptococci. 



Tbey may be arranged 



in bunches looking much 



like a cluster of grapes; 



when so grouped they 

 Fig. 10 streptococci, are Called staph vlococci. 



are many times found in large masses visible to the naked eye, 

 and are closely adherent to each other. Such masses are 

 zooiJ^lea. This condition is usually produced by the structure 



Fig. ]1. Staphylococci. 



Bacteria in general 



There seems to be a gelatinous 

 hydrated condition of the cell 



of the cell wall in such cases, 

 substance s iriourjdiug the cell due to a 

 wall. 



FISSION. 



The matter of fission or division in bacteria influences largely their 

 arrangement or grouping. It is easy to conceive a bacillus dividing in 

 two and these two in four and so on by constrictions which 

 singieFission. gradually separate the bacilli. If these constrictions are com- 

 plete, the bacilli will appear single, if not they will form in 

 threads. The same thing takes place with micrococci; if the 

 constrictions are complete, they are single; if not complete, they form 

 chains which correspond to threads of bacilli. By some authors these 

 words thread and chain are used synonymously. Should a micrococcus 

 divide and form two, a diplococcus would exist, but if these 

 two should divide in a direction opposite to the first, a group 

 of four or a tetrad would be formed. In this case there are 

 divisions in two directions. Now consider a division of the 

 cocci constituting the tetrad in a third direction, producing a 

 cub. shaped mass, the resulting group would be a sarcine. 

 Maitipiication. Through fission, multiplication of bacteria occurs. When 

 placed under proper conditions it is very rapid, in some species 

 every half huur. This increase in a geometrical ratio conveys some 

 notion of the number of bacteria one micro-organism will give rise to in 

 th«^ course of Iweuly-four hours. The multiplication would be like this: 

 At the beginning there is one bacillus. 



end of the first half hour there will be two bacilli. 



Double 

 Fieexon. 



Tripple 

 Fission. 



" second " 

 " third " 

 " fourth " 

 " fifth " 

 " sixth •' 



four " 

 eight " 

 sixteen bacilli, 

 thirty-two bacilli, 

 sixty-four 



" seventh half hour there will be one hundred twenty- 



