386 ELEMENTARY BIOLOGY. [CHAP. 



7. After treatment with ether and alcohol, and staining 

 with hasmatoxyHn solution, a single deeply-stained body, 

 probably of a nuclear nature, may be distinguished in 

 each cell. 



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. 



b. 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^. 



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. "^" will hardly grow at all, "(^" 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. 



^ See Appendix E, p. 494. 



