730 
PRODUCTION OF SEX. 
PRODUCTION OF SEX.* 
Referring to an article contributed by himself to a Venetian 
journal, in which he attributes the determination of the sexes 
to the number of spermatozoa which enter the ovum, M. 
Canestrini considers that experiments are needed in order to 
ascertain what amount of sperm is necessary for the pro¬ 
duction of each sex. M. Thury^s theory, that the lateness or 
earliness of the period of fertilisation is the determining cause, 
though not an exact theory, is yet favorable to that of the 
author; for the reason why fertilisation early in the period of 
heat of the female produces female offspring appears to be the 
distance at which the ovum then is from the source of the 
sperm, and the consequently small number of spermatozoa 
which penetrate so far up the Fallopian tube as to reach it. 
In some cases the sex may be said to be determined by 
accident, as when, of many sperm-cells produced, but few 
meet the ovum owing to a combination of unnoticed causes, 
and so a female offspring is the result. But given that the 
circumstances generally are favorable in both parents, and 
that the fertilisation takes place towards the end of the period 
of heat of the female, a male may be expected to be generated. 
On the other hand, a morbid condition or malformation of 
the female generative organs, or a scantiness of sperm in the 
male, should result in the production of a female. Among 
actual facts which bear out these theoretical considerations 
are cited twenty experiments made by Dr. Heitzmann; of 
these, twelve bore out the prediction previously made as to 
the sex to be expected. It is a known fact, confirmed by 
experiments made with poultry, that an old male generates 
more males than females, and vice versa with a young one. 
This may be explained, in accordance with the hypothesis, 
either on the assumption that the semen is more concentrated 
as a rule in an old male, or that copulations being less fre¬ 
quent in such cases, the spermatozoa would be more abun¬ 
dant. 
The ovum may develop without contact of semen, i. c. 
partheno-genetically, in which case the sex of the offspring 
will be always the same for the same species, or if receiving 
a minimum amount, will go through merely the primary stages 
of development, and will abort; or it may receive a greater 
amount and produce a female, or a still greater amount and 
a male will be the result.— Journ. Roy. Mic. Soc. 
# Bull . Soc. Ven.-Trent. Sci. Nat., i (1879), p. 18. 
