What did William Harvey study about animal reproduction?

William Harvey dedicated much of his later career to studying the nature of reproduction in animals, a field he explored in his 1651 work, Exercitationes de Generatione Animalium.12

His research included:

• Comparative Studies: He examined oviparous reproduction using chickens, where embryonic development occurs in eggs outside the mother, and viviparous reproduction using deer, where development occurs within the mother.1
• Epigenesis: Harvey was a proponent of the theory of epigenesis, which posits that the embryo is an undifferentiated form that gradually becomes specialized, rather than a preformed miniature individual.3
• Observational Detail: He investigated the roles of sperm and menstrual blood in embryo formation.1

While Harvey’s observational work was excellent and laid the foundation for modern embryology, he lacked the use of a microscope, which prevented him from fully resolving the complexities of these biological processes at the time.12