108 GENERAL BIOLOGY 



II. Reproduction. 



Bacteria reproduce chiefly by fission, hence the scientific 

 name of the order, Schizomycetes (Fission fungi). One 

 indication of this fission which may easily be observed is 

 the presence of chains or groups of bacteria. In what way 

 is this an evidence of division? 



HI. Physiology. 



Bacteria are plants but are not able to manufacture their 

 food as the green plants do. In order to grow they must 

 be in a medium which contains available food, and the 

 culture media used for their growth are so prepared as 

 to furnish the conditions necessary for their growth and 

 activity. 



1. Distribution of Bacteria. Methods of preparing the 

 nutritive media can be found in any of the manuals on bacter- 

 iology. With tubes or Petri dishes containing sterilized 

 gelatin make the following experiments : 



(a) Keep some carefully closed and labeled "not exposed." 



(6) Expose some to the air of the laboratory for three 

 minutes, and label accordingly. 



(c) Expose some to the dust from laboratory tables or 

 floor, or dust from the outside. 



(d) Let a drop of water from the laboratory tap flow over 

 another. 



0) Capture a fly and let it walk over the gelatin. 



Set these aside in a warm place and examine after a day 

 or two, noting what differences there are in the several 

 dishes. The small spots or patches probably present are 

 colonies of bacteria. Do they differ in form and color? 

 Examine the series still later. Have the colonies grown? 



