Abstract
Ringdoves given 10 parts per million p,p'-DDT showed a decrease of estradiol in the blood early in the breeding cycle and egg-laying was delayed. There was also a decrease in deposition of medullary calcium and in eggshell weight. Injection of p,p'-DDE (150 milligrams per kilogram of body weight) caused reduction of eggshell weight and inhibition of carbonic anhydrase in the oviduct.