of the Sexes nm Plants, Animals, and Man. 69 
ment of the male sex is always related to those general causes 
which induce a more complete maturation of the juices and a 
more perfect development of the organs. 
This fundamental fact the author applies to the animal king- 
dom. He refers, in the first place, to the fundamental identity 
of the two sexes—an identity which allows us to explain the 
characteristic differences of the sexes by simple differences in the 
mode and amount of development. He then seeks the causes of 
these differences, by analogy with plants, in the conditions 
which, at a certain moment (very near the first origin of the 
organism, since it is anterior to the determination of the sex), 
produce a more complete development in the case of a male, and 
a less advanced or less complete development in that of a female. 
It remained to fix the precise moment at which this primary 
determination of the sex takes place. This might be before 
fecundation, or during or after this act. In the former case, if 
the fecundation were retarded, this retardation, permitting a 
more complete development of the ovum, must generally in- 
duce the production of male individuals. Now, in bees, accord- 
ing to the observations of Huber, if the fecundation take place 
early, workers (i. e. females) are chiefly produced ; whilst, if the 
fecundation be retarded beyond the twenty-second day, all the 
eggs deposited are male eggs. According to M. Thury, the 
decisive moment for the production of the sex will therefore 
precede the act of fecundation. 
It is true that, in bees, the interpretation of the facts 1s very 
complex, partly on account of parthenogenesis, partly in conse- 
quence of some other peculiar circumstances in the reproduction 
of these insects. But the author also knew, from some previous 
experiments, that, in domestic poultry, the eggs last laid nearly 
always furnish the cocks of the clutch ; and he thought it pro- 
bable that the last eggs which detach themselves from the ovary 
of the fowl are those which have had the most time for matura- 
tion. These eggs are fecundated, as all physiologists are aware, 
during their passage through the upper part of the oviduct. 
Therefore here also, when the fecundation is retarded, males are 
the result. 
It was easy to apply the preceding data to the uniparous 
Mammalia. In these the ovum separates from the ovary at the 
commencement of the rutting-season, and it may be fecundated 
at any time during the whole period that the female continues 
in heat, and consequently when its maturation or development 
is more or less advanced. If the fecundation take place at the 
commencement of the period of heat, a female is the result ; if 
at the end of this period, a male. This is the conclusion which 
is fully justified by the experiments of M. Cornaz. 
