The title I have been asked to discuss is the Coordination' of Reproductive Processes and this implies that there are many structures and functions to be coordinated. Text-fig. 1 gives a general idea of what these structures and functions are. The basal region of the brain, known as the hypothalamus, is played upon by many stimuli from the external environment acting through different nerve tracts. The hypothalamus in turn regulates, through a system of small vessels, the secretory activity of the anterior pituitary gland, which for the purposes of reproduction secretes two or three gonadotrophic hormones into the bloodstream. These hormones are very largely, if not entirely, responsible for maintaining the activity of the ovary and the testis, and for varying and regulating the processes going on in the gonad. The gonad in turn secretes into the bloodstream simpler steroid hormones, which act upon the reproductive tract and the mammary glands.