Slide showing 'Diagram of the position of the presumptive optic cup and presumptive lens in the neurula stage.' Slide shows diagram of the position of the presumptive optic cup and presumptive lens in the neurula stage. Title below image reads 'Diagram of the position of the presumptive optic cup and presumptive lens in the neurula stage. (After [name omitted]).' Late 19th to early 20th century