1 88 
Psyche 
[December 
of the factors which might account for this may be that the oocytes 
increase in size during gestation so that at the time an older ootheca 
is removed the oocytes are larger when again subjected to gonadotropic 
hormone. The larger oocytes may contain greater amounts of reserve 
substances allowing for a more rapid maturation of the eggs. 
Since the period between the first and second ovulations is about 
70 days (table 1) it is evident from figure 10, showing the relatively 
O 
o 
30 
> • • 
• •• 
25 j 
20 1 
Pycnosce/us surinamensis 
15 - 
10 7 
5 1 
• • 
I 1 1 1 1 I 1 ' 1 1 l 1 1 1 1 l 1 i i 1 I 1 1 1 1 l 1 1 1 1 1 1 1 1 1 I 1 1 1 1 l i 1 1 1 I 1 1 1 1 l 1 1 1 1 1 
5 10 15 20 25 30 35 40 45 50 55 60 
AGE (DAYS) OF OOTHECA WHEN REMOVED FROM UTERUS 
Fig. 10. Relationship between the age of the ootheca at the time it was 
removed from the uterus of Pycnoscelus surinamensis (parthenogenetic strain) 
and the time required to form a new ootheca. Each point represents one 
individual. The points at 53 to 58 days on the x axis, are for females that 
gave birth normally; all of the other points are based on females that had 
their oothecae removed manually. 
rapid development of the oocytes (as indicated by oviposition) after 
removal of the ootheca, that the oocytes are inhibited by the presence 
of the eggs in the uterus. 
Virgin females of the bisexual strain of Pycnoscelus almost invari- 
ably fail to retract their oothecae into the uterus (Roth and Willis, 
1961 ) . Fourteen virgin females that had dropped their oothecae when 
they were formed, oviposited again in 28 to 39 days (x= 32 - 9 ±i.i 
days). The normal interval between the first and second ovulations 
in this strain is about 67 days (53 days of gestation plus 14 days 
postparturition, table 1 ) and the absence of uterine eggs in the brood 
sac resulting from aberrant oviposition hastened the development of 
