SEX.
With regard to the laws which regulate the sex of progeny very little
is known. Many and extensive observations have been made, but without
arriving at any definite conclusions. Nature seems to have provided
that the number of either sex produced, shall be nearly equal, but by
what means this result is attained, has not been discovered. Some
physiologists think the sex decided by the influence of the sire,
others think it due to the mother. Sir Everard Home believed the
_ovum_ or germ, previous to impregnation to be of no sex, but so
formed as to be equally fitted to become either male or female, and
that it is the process of impregnation which marks the sex and forms
the generative organs; that before the fourth month the sex cannot be
said to be confirmed, and that it will prove male or female as the
tendency to the paternal or maternal type may preponderate.
Mr. T.A. Knight[19] was of opinion that the sex of progeny depended
upon the influence of the female parent. He says, "The female
parent's influence upon the sex of offspring in cows, and I have
reason to believe in the females of our other domestic animals, is so
strong, that it may, I think, be pronounced nearly positive," He also
says, "I have repeatedly proved that by dividing a herd of thirty cows
into three equal parts, I could calculate with confidence upon a large
majority of females from one part, of males from another, and upon
nearly an equal number of males and females from the remainder. I have
frequently endeavored to change the habits by changing the male
without success." He relates a case as follows:--"Two cows brought all
female offspring, one fourteen in fifteen years, and the other fifteen
in sixteen years, though I annually changed the bull. Both however
produced one male each, and that in the same year; and I confidently
expected, when the one produced a male that the other would, as she
did."
M. Giron, after long continued observation and experiment, stated with
much confidence, that the general law upon this point was, that the
sex of progeny would depend on the greater or less relative vigor of
the individuals coupled. In many experiments purposely made, he
obtained from ewes more males than females by coupling very strong
rams with ewes either too young, or too aged, or badly fed, and more
females than males by a reverse choice in the ewes and rams he put
together.
Mon. Martegoute, formerly Professor of Rural Economy, in a late
communication to the "Journal D'Agriculture Pratique," says that as
the result of daily observations at a sheepfold of great importance,
that of the Dishley Mauchamp Merinos of M. Viallet at Blanc, he has,
if not deceived, obtained some new hints. He states that Giron's law
developed itself regularly at the sheepfold in all cases where
difference of vigor was observed in the ewes or rams which were
coupled; but he adds another fact, which he had observed every year
since 1853, when his observations began. This fact consists--
_First_, In that at the commencement of the rutting season when the
ram is in his full vigor he procreated more males than females.
_Second_, When, some days after, and the ewes coming in heat in great
numbers at once, the ram being weakened by a more frequent renewal of
the exertion, the procreation of females took the lead.
_Third_, The period of excessive exertion having passed, and the
number of ewes in heat being diminished, the ram also found less
weakened, the procreation of males in majority again commenced."
In order to show that the cause of such a result is isolated from all
other influences of a nature to be confounded with it, he gives the
details of his observations in a year when the number of births of
males and females were about equal. He also goes on to say, that, "at
the end of each month all the animals at the sheepfold are weighed
separately, and thanks to these monthly weighings, we have drawn up
several tables from which are seen the diminution or increase in
weight of the different animals classed in various points of view,
whether according to age, sex or the object for which they were
intended.
Two of these tables have been appropriated to bearing ewes--one to
those which have borne and nursed males and the other to those which
have borne and brought up females. The abstract results of these two
tables have furnished two remarkable facts.
_First_, The ewes that have produced the female lambs are, on an
average, of a weight superior to those that produced the males; and
they evidently lose more in weight than these last during the suckling
period.
_Second_, The ewes that produce males weigh less, and do not lose in
nursing so much as the others.
If the indications given by these facts come to be confirmed by
experiments sufficiently repeated, two new laws will be placed by the
side of that which Giron de Bazareingues has determined by his
observations and experiments. On the one hand, as, at liberty, or in
the savage state, it is a general rule that the predominance in acts
of generation belongs to the strongest males to the exclusion of the
weak, and as such a predominance is favorable to the procreation of
the male sex, it would follow that the number of males would tend to
surpass incessantly that of the females, amongst whom no want of
energy or power would turn aside from generation, and the species
would find in it a fatal obstacle to its reproduction. But, on the
other hand, if it was true that the strongest females and the best
nurses amongst them produce females rather than males, nature would
thus oppose a contrary law, which would establish the equilibrium, and
by an admirable harmony would secure the perfection and preservation
of the species, by confiding the reproduction of either sex to the
most perfect type of each respectively."
FOOTNOTES:
[19] Philosophical Transactions, 1809.