228 



BESSIE NOTES 



Five months later (in June, 1919), among another 100 or- 

 ganisms isolated under the same experimental conditions, 42 lived 

 for 7 days, 39 for 6 days, 15 for 5 days, 2 for 4 days, and 2 for 

 3 days, giving an average length of life of 6.17 days. This 

 increase in the length of life, accompanied by a marked increase 

 in the number of eggs deposited, formed the basis for an experi- 

 ment in selection in an attempt to increase both of these factors 

 beyond the limits indicated above, as detailed in a later section. 

 A tabulation of 1200 individuals reared at laboratory tempera- 

 ture (47° to 63°F.) in ^ per cent malted milk at various times 

 during the study shows that 295 lived for 7 days, 357 for 6 days, 

 382 for 5 days, 127 for 4 days, 35 for 3 days, and 4 for 2 days, 

 giving an average length of life of 5.60 days (table 1). Under 

 these conditions, with food constant and temperature variable, 

 the individual range of life was from two to seven days with an 

 average life cycle of 5.47 days for 1400 individuals. In an 

 experiment with 254 organisms isolated in xe per cent malted 

 milk and kept constantly at 23° to 25°C., it was found that 9 

 lived for 7 days, 56 for 4 days, 84 for 5 days, 60 for 4 days, 33 

 for 3 days, 10 for 2 days, and 2 for 1 day, giving an average 

 length of life of 4.68 days. 



TABLE 1 



A table of the length of life of 1200 individuals (100 in a group) reared in xt per cent 

 malted milk at laboratory temperature 



