LIFE CYCLE OF HYDATINA SENTA 297 
They laid 298 eggs, none of which hatched before August 10, at 
which time they were discarded. <A portion of this lot of eggs was 
kept cool (11° C.) for over seven weeks and then brought to room 
temperature; and another portion was frozen for thirty-three 
hours and then gradually thawed out. But none of these eggs 
hatched within twelve weeks, after which time observations 
ceased. 
The F, females mentioned in the same paper (op. cit.) were 
inbred, but of 146 eggs laid, none hatched in seven weeks. Like- 
wise, in the cross between F; and the Baltimore parent line, 
which were related lines, of 179 eggs none hatched in seven weeks. 
In the cross between F, and the New York parent line (also re- 
lated lines), of 814 eggs, two hatched in about a week, while 
no more hatched in the next seven weeks. ; 
In the above cases there is great variability in the duration of 
the egg stage in eggs coming from the same source; and there is 
considerable difference between eggs coming from one source 
and those from another source. Thus, crosses between unrelated 
lines yielded the greatest percentage of viable eggs; crosses 
between related lines yielded few or no viable eggs, while inbreed- 
ing failed to produce eggs that would hatch at all. 
Since that time I have obtained numerous viable ‘inbred’ 
eggs, and crosses that produced a much higher percentage of 
viable eggs; but in none of these cases were complete records 
kept, hence comparative figures are not available. 
It has already been demonstrated (Shull, ’11 a) that fertilized 
eggs from different sources may yield parthenogenetic lines 
including different proportions of male-producers. The great 
variability in the duration of the egg stage in eggs from the same 
source, described above, suggested that this variability might 
be related to the proportion of male-producers in the partheno- 
genetic lines derived from those eggs; that is, that parthenogenetic 
lines derived from eggs that hatched quickly might include more 
or fewer male-producers than lines derived from late-hatching 
eggs. The following experiments were performed to test this possi- 
bility. The eggs used are the ‘inbred’ eggs obtained by pairing 
males and females of the same line (the ‘original line’ in Experi- 
ment 1). 
