Date of this Version
Alder, H. E. (1935). Determining the sex of day old chicks (University of Nebraska Agricultural Experiment Station Circular No. 51)
More than 2,000 years ago people were interested in determining the sex of the embryo in hatching eggs and the sex of day-old chicks. No method of determining the sex of day-old chicks (except of course in sex-linked chicks) was of the slightest value until the Japanese method was discovered and developed. About 1925 Japanese scientists discovered the presence of a rudimentary copulatory organ located on the ventral rim of the cloaca which was present in all day-old males and only a few day-old females.