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AN INTRODUCTION TO MODERN GENETICS 



closing the containers it is important to see that there are no folds 

 against the glass, which may form channels through which the flies 

 can creep out and escape. Cardboard stoppers may also be used, but 

 must be punched with small holes to provide ventilation. 



b. Food 



Standard food mixtures are as follows : 



I. Banana-agar food (for stocks). 



Water 



Chopped agar 

 Mashed bananas . 



1,000 c.c. 



25 grm. 

 1,000 grm. 



Boil the agar and water until dissolved, and add the thoroughly mashed 

 bananas. The latter may be made from overripe fruit, which can often 

 be purchased very cheaply. 



Dissolve agar before adding the other constituents, and boil all together 

 a short time. 



3. High productivity food (for 



Water . .. 



Agar 



Dry yeast . . 



Mashed raisins 



Syrup or treacle 



Semolina . . 



getting maximum offspring from crosses), 



800 c.c. 

 15 grm. 

 15 grm. 

 40 grm. 

 50 grm. 

 50 grm. 



Dissolve agar in boiling water and add yeast, boil for a ftirther ten 

 minutes before adding raisins, syrup, and semolina. 



c. Preparation of Culture Vessels 



To keep down pests (mites and molds) it is advisable to steriUze the 

 vessels before use, but this is not essential. It can easily be done by 

 heating to 130° C. for half an hour in an oven, but temperature changes 



