The genetic and the operative evidence relating to secondary sexual characters

"The Genetic and the Operative Evidence Relating to Secondary Sexual Characters" by T.H. Morgan, is a close look at how genetics and body functions affect the different physical traits between male and female birds. The text mainly focuses on exploring examples found Sebright bantams and other types of chickens. The details cover experiments and discoveries about what makes the feathers of male and female birds different, like how their inherited traits and hormones work, and why. Early in the book, the presence of hen-feathered and cock-feathered males within specific poultry breeds is presented, followed by a description of the author's experiments, including castrating hen-feathered Sebrights to notice plumage changes, and the observed physical changes in feathers after the birds were operated on.