Slide showing six diagrammatic drawings illustrating 'development of the optic cup and lens in Siredon pisciformis.' Slide shows six diagrammatic drawings illustrating 'development of the optic cup and lens in Siredon pisciformis' (a type of newt which is related to the Mexican salamander). Diagrams are labelled 'a' to 'f'. Title below slide reads: 'Fig. 21. a-f Development of the optic cup and lens in Siredon pisciformis. (After Rabl, 1898).' Late 19th to early 20th century