Mr Ritchie on ascertaining the Sex of the Chick in Ovo. 265 
Eggs were selected, all having the air-cell situated exactly 
on the apex of the larger end, and were hatched. In most in- 
stances, the birds were all males. 
Eggs were selected, all having the air-cell situated, not on, 
but near to the apex of the larger end. In most instances, the 
birds were all females. 
These experiments have been frequently repeated, and were 
conducted for me by persons residing in different parts of the 
country. 
A few of the experiments were not quite so satisfactory as 
the others. Among a dozen of birds of one brood, two or three 
turned out to be of a different sex from the rest. I may re- 
mark, however, that it is sometimes rather difficult to determine 
whether the air-cell be exactly on the apex or not; and the ano- 
maly may have originated in error arising from this cause. 
Every person has observed the air-cell in the boiled egg 
upon removing the shell : in the recent egg it may be perceived 
by holding the egg between the eye and a lighted candle. In 
general even an unpractised observer may determine the posi- 
tion of the cell, whether it be at the axis or some little way from 
it, and so conjecture the sex of the future bird. Occasionally, 
however, as already remarked, it is rather difficult to decide 
whether the air-cell is or is not on the axis. Such eggs should 
not be used by those who may be induced to put the criterion 
to the test of experiment. 
The fact ascertained by these experiments seems to deserve 
the attention of the economist and of the physiologist. 
At present I would only remark, that the result militates 
against an opinion, which has been ably defended, in regard to 
the ova of quadrupeds, and which has been advanced, too, as 
to the eggs of birds, That previous to impregnation, they have 
no distinction of sex, but are so formed as to be equally fitted to 
become male or female ; and that it is the process of impregna- 
tion which marks the distinction. 
The air-cell exists in unfecundated eggs. In some of these it 
is situated at the top of the larger end ; in others near the top. 
From this it would appear, that the male parent does not in- 
fluence the sex of the embryo, but that the ovum has assumed 
its sex previous to impregnation. 
2 
