Slide showing two drawings of 'a piece of the presumptive eye region from an early neurula of Bombinator'. Slide shows two drawings of 'a piece of the presumptive eye region from an early neurula of Bombinator'. Drawings are labelled 'a' and 'b', and provided with the following explanation: 'Fig 25 - a and b, a piece of the presumptive eye region from an early neurula of Bombinator (a) is grafted into the flank of another embryo of similar age (b). (After Spemann, 1919.)' Late 19th to early 20th century