478 
Bulletin Xo. 102.—1915. 
The Ratio of Bisexual to Unisexual Broods and the Rela¬ 
tion of Sex to the Order of Laying of the Eggs* 
Domestic pigeons ordinarily lay two eggs at each nesting, and it 
is another prevalent notion among pigeon breeders that these always, 
or at least in a majority of instances, give rise to a pair of squabs, 
that is, to one of each sex. Furthermore, it is commonly maintained 
that the first egg of the two laid produces a male, while a female is 
hatched from the second egg of the clutch. This belief is not only 
firmly established now, but goes far back into antiquity, for Aristotle 
(1910, 562 b ) has the following to say on the subject. “Birds of the 
pigeon kind, such as the ring-dove and the turtle-dove, lay two eggs 
at a time; that is to say, they do as a general rule, and they never 
lay more than three.” “The hen-pigeon, as has been said, occasion¬ 
ally lays three eggs, but it never rears more than two chicks, and some¬ 
times rears only one; and the odd one is always a wind-egg. ”* “The 
pigeon, as a rule, lays a male egg and a female egg, and generally lays 
the male egg first; after laying it allows a day’s interval to ensue and 
then lays the second egg. ” 
A point as interesting as this could scarcely be expected to escape 
Darwin, and indeed in connection with his statements previously 
referred to (Darwin, 1875, p. 247) he has the following to say on this 
matter: “Usually the two birds reared from the two eggs laid in 
the same nest are a male and a female; but Mr. Harrison Weir, who 
has been so large a breeder, says that he has often bred two cocks 
from the same nest, and seldom two hens.” Little serious attention 
appears to have been given to settling the matter, however, until it 
was taken up by Cuenot. This author first gives the subject con¬ 
siderable attention in a general paper on the determination of sex ' 
in animals (Cuenot, 1899) and reviews the literature up to his time. 
Most of his references have been inaccessible to us, but for the sake 
of completeness we include a summary of the observations and the 
citations to the original sources as given by him. 
♦The term "wind-egg” was formerly applied loosely to any imperfect, soft-shelled, unimpregnated 
or addled egg; its use is now obsolete. 
