520 CONTROLLING SEX IN BUTTERFLIES. 
those which are impregnated at the will of the mother produce 
females either partly or fully developed, i.e., workers, or queens. 
The rule with animals is that the ova perish unless vitalized by 
the direct influence of the male spermatozoa. Nevertheless par- 
thenogenesis in many of the lower forms of animal life, and espe- 
cially in insects, is an admitted fact; and what does it imply? 
To my mind it implies that in exceptional cases, the male ele- 
ment is sufficiently potent to vitalize the ova in the second gener- 
ation, or that it may endure until succeeding generations ; that, in 
short, to use Owen’s words, “the spermatic virtue of the ancestral 
coitus” may influence the descendants. Von Siebold does not ac- 
cept this explanation, but there are many facts which indicate 
that it is the true one, and the male element becomes exhauste 
in time and is needed sooner or later for the continuance of the 
species. 
Parthenogenesis has repeatedly occurred in species which nor- 
mally cannot multiply without direct sexual intercourse, e. g., in 
Bombyx mori, Sphinx ligustri, etc.; while in a great number of 
others the embryo, in eggs not directly fecundated, develops up to 
different stages. What in some species is the exception becomes 
the rule with others, of which the hive-bee is an example. The 
male element may be said to possess all degrees of potency in its 
influence on the reproductive function of its immediate issue, as 
the embryo in ova not directly fecundated attains all degrees of 
development before death. In cases of parthenogenesis it is potent 
enough, vital enough—to cause full development of the offspring 
for one or more generations, though, in the majority of instances, 
and especially where this mode of reproduction does not occur 
as a rule, this offspring is most frequently male. Finally, it may 
be so potent, as in what is termed thelotoky, that females instead 
of males are produced. 
The ova in a virgin queen bee may, therefore, be said to be al- 
ready partially fecundated — sufficiently so to produce males or 
drones ; but they must be more thoroughly vitalized, by the direct 
male influence, before the female sex can be stamped upon them. 
Even here, however, the sex is not changed after the deposition of 
the eggs, and it is not the influence of food which produces the 
hange, 
Though I believe that the evidence is against Mrs. Treat’s con- 
clusion, I hope she will continue her experiments, with that thor- 
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