1. A purebred Barred Plymouth Rock pullet, designated as "Kansas 1050," which at first appeared normal, later assumed plumage much more resembling that of a normal male, and became much like a capon in general appearance. 2. This change in secondary sexual characters was obviously due to the development of a very large ovarian tumor. 3. Implantation of ovarian tissue from a normal pullet produced an immediate effect on new plumage assumed. New feathers grown in the few weeks succeeding the operation were definitely hen feathers. 4. The "male" feathers assumed early in life as a result of the pathological condition of the ovary, though like normal male feathers in shape and structure, resembled hen feathers in respect to barring. This distinguishes clearly the difference between secondary sexual dimorphism, as exhibited in the first instance, and dimorphism caused through sex linkage, as illustrated by the barring.