38 THE BIOLOGY OF THE CELL 



which has been sterilized by being passed through 

 the flame of the lamp, take up a few drops of the 

 fluid in the teacup, and mix them with the Pas- 

 teur's fluid in the test-tube. Set the test-tube in 

 a warm place, e. g., 35° C, for a few hours, exam- 

 ining from time to time to see if bubbles of gas 

 are formed. Is the actual presence of yeast cells 

 necessary to produce fermentation, or is there 

 something in the fluid in which yeast cells have 

 lived which will bring about that change? If 

 the latter, whence does that something — i. e., en- 

 zyme or ferment — probably come ? 



i. Reproduction. 



1. Budding or gemmation. — Examine cells from 



each of the cultures made in the experiment 

 on the effect of food-supply upon growth. In 

 which have the cells the largest number of 

 buds ? In which the smallest ? How many 

 buds may a cell have? Do all the cells have 

 buds? Can you always distinguish which is 

 the " parent " and which is the " bud " ? Are 

 the buds always formed on the same part of the 

 cell ? "What are the steps in the process of the 

 formation of a bud ? "What is the difference 

 between reproduction by budding and repro- 

 duction by fission? Is the difference funda- 

 mental ? 

 Make drawings to show how buds are formed and how 

 they are attached. 



2. Endogenous spore-formation. — Make a slab c>f 



plaster of Paris about one-fourth of an inch in 

 thickness and about two inches square. Upon 

 one face of this paint with a clean camel's-hair 



