318 HEREDITARY ADAPTATION TO HIGHER TEMPERATURE 



added to the flask, the excess water was absorbed by the addition of absorbent 

 cotton, and the flask sterilized. It is important to add sufiicient cotton to absorb 

 the water as otherwise the insects stick to the side of the flask and are drowned. 

 In order to transfer the culture, the flask is connected to one containing the insects 

 by means of the side tubes, using the same technique as in handhng a Pasteur 

 flask. The flies are then shaken from one flask to the other through the connect- 

 ing side tubes, the flasks disconnected, and the connecting tubes flamed and re- 

 plugged. In this way the organisms can be handled with as little danger of in- 

 fection as cultures of bacteria. 



SUMMARY. 



1. Images of Drosophila raised at temperatures of from 12-28.5°C. 

 when placed at any temperature from 15-32.5°C. produce eggs which 

 develop normally at these temperatures. 



2. Imagos raised at temperatures of from 29-32.5° and then kept 

 permanently within these temperatures produce eggs which do not 

 develop. 



3. Imagos raised at from 28.5-32. 5°C. and then placed at tem- 

 peratures of from 12-25°C. produce eggs which develop normally. 



4. Imagos raised at from 28,5-32.5°C. placed at 15-25°C. for 

 24 hours or longer and then put back into a temperature of 

 from 28.5-32,5°C., produce eggs which will develop at the latter 

 temperature. 



5. There is no evidence of any hereditary adaptation to higher 

 temperatures. 



