Development of the nervous system in humans optical vesicle (which will eventually become the optic nerve, retina and iris) forms at the basal plate of the prosencephalon. In the fifth week, the alar plate of the prosencephalon expands to form the cerebral hemispheres (the telencephalon). The basal plate becomes the diencephalon. The diencephalon, mesencephalon and rhombencephalon constitute the brain stem of the embryo. It continues to flex at the mesencephalon. The rhombencephalon folds posteriorly, which causes its alar plate to flare and form the fourth ventricle of the brain. The pons and the cerebellum form in the upper part of the rhombencephalon, whilst the medulla oblongata forms
Where the Boys Are to head the cast." Natalie Wood, who had just made "All the Fine Young Cannibals" for MGM, was mentioned as a possible star at one stage. MGM eventually persuaded the book's author to change the title from "Unholy Spring" to "Where the Boys Are". Henry Levin was signed to direct. The first two stars confirmed for the movie were George Hamilton and Yvette Mimieux. Paula Prentiss was cast despite never having made a movie before. Connie Francis also made her movie debut. The novel contained a section where the students help raise money to ship arms to Fidel Castro for