LIFE CYCLE OF HYDATINA SENTA 299 
This possible decrease can hardly be urged in this case, however, 
as a reason for assuming that the effect of late hatching is even 
greater than table 5 shows it to be. For the ‘early-hatched’ 
line is here taken at a period of many male-producers. Prior 
to the opening of this experiment, the early hatched line included 
16 generations. If these 16 generations be included with the 
12 generations in table 5, the total for the early hatched line is 
147 male-producers and 732 female-producers, or 16.7 per cent of 
male-producers. This is not greatly in excess of the 15.4 per cent 
in the late hatched line. 
It may be pointed out incidentally that the average size of 
family in the late hatched line exclusive of the last family which 
was not fully recorded, is 26.8. In the early hatched line, if we 
count only the generations given in table 5, the average size of 
family is 25; but if the 16 earlier generations be included, the 
average size of family is 30.7. There is perhaps here a decrease 
of vigor associated with duration of the egg stage. 
Experiment 4. Of the same lot of fertilized eggs as that used 
in the preceding experiment, one hatched after not less than 75 
days nor more than 91 days in the egg stage, which is a much 
longer time than most of the other eggs of the same lot required. 
A line of 12 generations was bred from this individual, and is 
given in the right column of table 6. No line derived from an 
early hatching egg of this same lot was in existence at that time 
to compare with the late hatching line. The ‘original line’ (of 
Experiment 1) from which the lot of inbred eggs was obtained 
was still being reared, and that part of it which occurred simul- 
taneously with the late hatched line in table 6 is given for com- 
parison; but the original line isso much older than the late hatched 
line that we should expect it to have fewer male-producers even 
if it were at first equal to the late hatching line in the proportion 
of male-producers. This expectation is justified by the percent- 
ages in the table, where the original line gives only 9.4 per cent 
of male-producers, whereas the entire original line, including 39 
generations previous to the seven here given, gave 17.3 per cent 
of male-producers. This is only a little less than the percentage 
obtained from the late hatching egg. It should also be recalled 
