Regnier de Graaf was one of the most prominent scientists and physicians of the 17th century. He made significant contributions to reproductive and anatomical research.
Regnier de Graaf initially thought that ovarian follicle was the egg itself.
Under the misconception that the egg itself travels to the uterus through the fallopian tube, de Graaf also proposed a new theory of sexual reproduction, the ovist theory, that stated that the spermatozoa or the sperm contains the "spirit of life" that it infuses into the egg.
The <em>ovist </em>theory is one of the forms of preformationism, the other being the <em>spermist </em>theory. Both of these regard the egg or the sperm to be containing the "spirit of life" or the embryo.
His discovery of the ovarian follicle (known as Graafian follicle) that ruptures to release the egg later changed his point of view.
