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Psyche 
[December 
in virgin females prior to the first pregnancy, and severance of the 
nerve cord may affect the ability of the female to oviposit but has no 
influence on the rate of maturation of the oocytes. There is no inhibi- 
tory center in the last abdominal ganglion in this species before the 
first oviposition. The insertion of wax into the uterus, after removal 
of the ootheca, results in inhibition of the corpora allata, and indi- 
cates that a chemical substance from uterine eggs is not necessary for 
inhibition of corpora allata in Pycnoscelus. We interpret these results 
to mean that pressure from the stretched uterus regulates the secretion 
of the corpora allata. As suggested by Engelmann (1962) the inhibi- 
tory center may be caudal to the site of the operation and “the brain 
may act only as a way station for the transmission of nervous impulses.” 
In Rhodnius prolixus the release of brain hormone was triggered by 
the distension of the insect’s abdomen following a blood meal. Since 
cutting the nerve cord eliminated this effect, Wigglesworth (1934) 
inferred that the neurosecretory cells were influenced by nerve impul- 
ses arising in abdominal proprioceptors. The two stretch receptors 
found in each abdominal segment of Rhodnius adapt scarcely at all 
and will continue to discharge as long as the abdomen is stretched 
(Van der Kloot, 1961). In all of the false ovoviviparous cockroaches 
the uterus becomes greatly distended as the eggs increase in size as a 
result of water uptake and growth (Roth and Willis, 1955). It is pos- 
sible that inhibition of the oocytes during pregnancy may be due to 
pressure on abdominal stretch receptors as in Rhodnius. However, it 
is also conceivable that there are mechanoreceptors in the uterus itself. 
The present evidence indicates that the ovipositor is not involved in 
transmitting the pressure stimulus from the ootheca in the uterus or 
genital chamber of Pycnoscelus and Byrsotria ; similarly, the ovipositor 
in Blattella germanica is not involved in corpora allata inhibition while 
the female carries its egg case (Roth and Stay, 1962). 
In Blattella which carries its ootheca externally, and in all cock- 
roaches that incubate their eggs internally, the ootheca swells during 
embryogenesis, particularly in the latter species (Roth and Willis, 
1955, 1 955a, 1958). We (Roth and Stay, 1959, 1961, 1962) 
have suggested that during pregnancy inhibition of the corpora allata 
is due to nervous stimuli resulting from pressure of the ootheca. The 
changing pressure stimulus resulting from the increase in size of the 
ootheca would tend to prevent or retard adaptation of the receptors 
involved so that the corpora allata are inhibited during the entire 
(except in Diploptera and some Nauphoeta) gestation period. How- 
ever, in virgins of Blattella germanica (Roth and Stay, 1962) 
Blaberus craniifer, Byrsotria fumigata, and Pycnoscelus surinamensis 
