﻿386 ELEMENTARY BIOLOGY. [CHAP. 



8. [Sow a few yeast-cells in Pasteur's solution in a moist 

 chamber and keep them under observation from day to 

 day ; watch their growth and multiplication.] 



9. [Spore-formation : take some dry German yeast ; sus- 

 pend it in water and shake so as to wash it. Let the 

 mixture stand for half-an-hour : pour off the super- 

 natant fluid, and, with a camel's hair pencil, spread out 

 the creamy deposit in a thin layer on fresh cut potato 

 slices or on a plate of plaster of Paris, and place with 

 wet blotting-paper under a bell-jar : examine from day 

 to day with a very high power (800 diam.) for spores, 

 which will probably be found on the eighth or ninth 

 day.] 



B. PHYSIOLOGY. 



(Conditions and results of the vital activity of Torula.} 

 i. Sow a fair-sized drop of yeast in - 

 a. Distilled water. 

 I. 10 per cent, solution of sugar in water. 



c. Pasteur's fluid without the sugar. 



d. Pasteur's fluid with sugar. 

 [e. Mayer's pepsin solution 1 .] 



Keep all at about 35 C., and compare the growth of the 

 yeast, as measured by the increase of the turbidity of the 

 fluid, in each case, "a" will hardly grow at all, "b" better, 

 "<:" better still, "^" well, and "e" best of all. Note that 

 bubbles of gas are plentifully evolved from both the so- 

 lutions which contain sugar. 



1 Mayer's solution (with pepsin) = 



15 per cent, solution of sugar-candy 20 cc. 



Dihydropotassic phosphate o* i grm. 



Calcic phosphate o' i grm. 



"Magnesic sulphate o' i grm. 



Pepsin 0-23 grm. 



