232 BESSIE NOTES 



with difficulty; but such a comparison must be made with reser- 

 vation, owing to the absence of any such eggs during the winter 

 of 1919-1920, although some cultures were under the same condi- 

 tions of environment as during the previous winter. On the 

 other hand, such thick-shelled forms may have been deposited 

 by fertilized females and have never appeared in later cultures, 

 since all forms produced in malted milk have been females and 

 there has hence been no possibility of fertilization taking place. 



An individual usually deposits an egg during the first twenty- 

 four hours of its life, and the average daily rate of production 

 determined for 1500 individuals isolated in ys per cent malted 

 milk was 1 egg the first day, 3 the second, 5 the third, 7 the 

 fourth, 3 the fifth, and 1 the sixth. There is, however, much 

 variation in different individuals, as will be seen from table 2, 

 which gives the daily egg production for fifty specimens in 

 February, 1919, and for fifty specimens five months later in 

 June, 1919. 



As the table shows, there is an individual range of about 1 to 

 10 eggs for every day of the egg-laying period. If the number 

 of eggs deposited on the first day is high (7 to 9), the life-cycle is 

 usually shortened to three to five days, but if the number is 

 small (1 to 3) on the first day and increases gradually on the 

 second and third days, the life-cycle is longer (five to seven days) 

 and in many cases the egg production higher. For 1200 indi- 

 viduals in YE per cent malted milk at room temperature (47° to 

 63°F.) the average total egg production was 19.56. For 254 

 individuals in jt per cent malted milk at a constant temperature 

 of 23° to 25°C. the average total egg production was 17.37. This 

 decrease in number of eggs was associated with a decrease in the 

 average length of life from 5.60 days to 4.68 days, as has been 

 noted earlier in the paper. For 100 individuals isolated early 

 in the study the average total egg production was 12.79, while the 

 average production of an equal number of individuals a few 

 months later was 23.43 eggs per individual. This increase in 

 average egg production was associated with an increase in the 

 average length of life from 4.65 days to 6.17 days. This marked 

 difference in egg production and length of life in two groups of 



