GENERAL BIOLOGY 



for two or three days. Examine the tubes from day to day and 

 judge, from microscopic examination and the turbidity, in which 

 fluid the yeast grows best. In which are the most bubbles of gas 

 formed? Does the formation of gas bear any relation to the 

 growth? This is saprophytic nutrition. 



2. Reproduction, (a) Budding. With the microscope examine 

 cells from each of the test tubes. In which have the cells the largest 

 number of buds? In which the smallest? How many buds may 

 a cell have? Show by drawings the steps in the formation of a 

 mature bud. What is the difference between budding and fission? 

 (b) Endogenous Spore Formation sometimes occurs in yeast, but 

 is difficult to observe and may be omitted from your notes. 



3. The effect of growth of yeast upon food supply, (a) Taste 

 of the Pasteur's solution with sugar in which yeast has been acting 

 for a day or two. Compare with a solution in which there is no 

 yeast. How do you explain the difference? (b) Examine the 

 distillate of a solution containing sugar in which yeast has been 

 growing for a day or two. Notice that it has the taste and odor, 

 and burns with a pale blue flame, characteristic of alcohol, (c) 

 Nature of the gas given off. Take two test tubes, fill the first y$ 

 full of clear baryta water, fill the second about ^> full of yeast 

 which is actively giving off bubbles of gas. Insert a cork in this 

 second tube and connect the two by a bent glass tube, one end 

 of which passes through the cork into the air space above the 

 yeast, the other end of which dips below the surface of the baryta 

 water. What changes take place in the baryta water? This is a 

 test for carbon dioxide, (d) Chemical reaction of fluid yeast. 

 Determine by the use of litmus paper whether fluid yeast is acid 

 or alkaline in its nature. What do you suppose the cause of this 

 to be? 



Prepare a written statement giving as far as possible an explana- 

 tion of all the facts you have observed in the experiments in this 

 section. 



BACTERIA. 

 (Division-Thallophyta, Subdivision Fungi, Class Schizomycetes.) 



Read: Calkins, Biology, pp. 34-43 or 



Parker, Elementary Biology, pp. 82-94; or 



Sedgwick and Wilson, General Biology pp. 192-204; or 



Woodruff, Foundations of Biology, pp. 44-53. 



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